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• Visual C++ - Memory Leak Detection

  - by Jacob

  Any suggestions? This SO post talks about Visual Leak Detector, but I'm looking for other tools. Also, please don't recommend this.

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• Question about unions and heap allocated memory

  - by Dennis Miller

  I was trying to use a union to so I could update the fields in one thread and then read allfields in another thread. In the actual system, I have mutexes to make sure everything is safe. The problem is with fieldB, before I had to change it fieldB was declared like field A and C. However, due to a third party driver, fieldB must be alligned with page boundary. When I changed field B to be allocated with valloc, I run into problems. Questions: 1) Is there a way to statically declare fieldB alligned on page boundary. Basically do the same thing as valloc, but on the stack? 2) Is it possible to do a union when field B, or any field is being allocated on the heap?. Not sure if that is even legal. Here's a simple Test program I was experimenting with. This doesn't work unless you declare fieldB like field A and C, and make the obvious changes in the public methods. #include <iostream> #include <stdlib.h> #include <string.h> #include <stdio.h> class Test { public: Test(void) { // field B must be alligned to page boundary // Is there a way to do this on the stack??? this->field.fieldB = (unsigned char*) valloc(10); }; //I know this is bad, this class is being treated like //a global structure. Its self contained in another class. unsigned char* PointerToFieldA(void) { return &this->field.fieldA[0]; } unsigned char* PointerToFieldB(void) { return this->field.fieldB; } unsigned char* PointerToFieldC(void) { return &this->field.fieldC[0]; } unsigned char* PointerToAllFields(void) { return &this->allFields[0]; } private: // Is this union possible with field B being // allocated on the heap? union { struct { unsigned char fieldA[10]; //This field has to be alligned to page boundary //Is there way to be declared on the stack unsigned char* fieldB; unsigned char fieldC[10]; } field; unsigned char allFields[30]; }; }; int main() { Test test; strncpy((char*) test.PointerToFieldA(), "0123456789", 10); strncpy((char*) test.PointerToFieldB(), "1234567890", 10); strncpy((char*) test.PointerToFieldC(), "2345678901", 10); char dummy[11]; dummy[10] = '\0'; strncpy(dummy, (char*) test.PointerToFieldA(), 10); printf("%s\n", dummy); strncpy(dummy, (char*) test.PointerToFieldB(), 10); printf("%s\n", dummy); strncpy(dummy, (char*) test.PointerToFieldC(), 10); printf("%s\n", dummy); char allFields[31]; allFields[30] = '\0'; strncpy(allFields, (char*) test.PointerToAllFields(), 30); printf("%s\n", allFields); return 0; }

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• SQL SERVER – Weekly Series – Memory Lane – #003

  - by pinaldave

  Here is the list of curetted articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2006 This was the first year of my blogging and lots of new things I was learning as I go. I was indeed an infant in blogging a few years ago. However, as time passed by I have learned a lot. This year was year of experiments and new learning. 2007 Working as a full time DBA I often encoutered various errors and I started to learn how to avoid those error and document the same. ERROR Msg 5174 Each file size must be greater than or equal to 512 KB Whenever I see this error I wonder why someone is trying to attempt a database which is extremely small. Anyway, it does not matter what I think I keep on seeing this error often in industries. Anyway the solution of the error is equally interesting – just created larger database. Dilbert Humor This was very first encounter with database humor and I started to love it. It does not matter how many time we read this cartoon it does not get old. Generate Script with Data from Database – Database Publishing Wizard Generating schema script with data is one of the most frequently performed tasks among SQL Server Data Professionals. There are many ways to do the same. In the above article I demonstrated that how we can use the Database Publishing Wizard to accomplish the same. It was new to me at that time but I have not seen much of the adoption of the same still in the industry. Here is one of my videos where I demonstrate how we can generate data with schema. 2008 Delete Backup History – Cleanup Backup History Deleting backup history is important too but should be done carefully. If this is not carried out at regular interval there is good chance that MSDB will be filled up with all the old history. Every organization is different. Some would like to keep the history for 30 days and some for a year but there should be some limit. One should regularly archive the database backup history. South Asia MVP Open Days 2008 This was my very first year Microsoft MVP. I had Indeed big blast at the event and the fun was incredible. After this event I have attended many different MVP events but the fun and learning this particular event presented was amazing and just like me many others are not able to forget the same. Here are other links related to the event: South Asia MVP Open Day 2008 – Goa South Asia MVP Open Day 2008 – Goa – Day 1 South Asia MVP Open Day 2008 – Goa – Day 2 South Asia MVP Open Day 2008 – Goa – Day 3 2009 Enable or Disable Constraint  This is very simple script but I personally keep on forgetting it so I had blogged it. Till today, I keep on referencing this again and again as sometime a very little thing is hard to remember. Policy Based Management – Create, Evaluate and Fix Policies This article will cover the most spectacular feature of SQL 2008 – Policy-based management and how the configuration of SQL Server with policy-based management architecture can make a powerful difference. Policy based management is loaded with several advantages. It can help you implement various policies for reliable configuration of the system. It also provides additional administrative assistance to DBAs and helps them effortlessly manage various tasks of SQL Server across the enterprise. SQLPASS 2009 – My Very First SQPASS Experience Just Brilliant! I never had an experience such a thing in my life. SQL SQL and SQL – all around SQL! I am listing my own reasons here in order of importance to me. Networking with SQL fellows and experts Putting face to the name or avatar Learning and improving my SQL skills Understanding the structure of the largest SQL Server Professional Association Attending my favorite training sessions Since last time I have never missed a single time this event. This event is my favorite event and something keeps me going. Here are additional post related SQLPASS 2009. SQL PASS Summit, Seattle 2009 – Day 1 SQL PASS Summit, Seattle 2009 – Day 2 SQL PASS Summit, Seattle 2009 – Day 3 SQL PASS Summit, Seattle 2009 – Day 4 2010 Get All the Information of Database using sys.databases Even though we believe that we know everything about our database, we do not know a lot of things about our database. This little script enables us to know so many details about databases which we may not be familiar with. Run this on your server today and see how much you know your database. Reducing CXPACKET Wait Stats for High Transactional Database While engaging in a performance tuning consultation for a client, a situation occurred where they were facing a lot of CXPACKET Waits Stats. The client asked me if I could help them reduce this huge number of wait stats. I usually receive this kind of request from other client as well, but the important thing to understand is whether this question has any merits or benefits, or not. I discusses the same in this article – a bit long but insightful for sure. Error related to Database in Use There are so many database management operations in SQL Server which requires exclusive access to the database and it is not always possible to get it. When any database is online in SQL Server it either applications or system thread often accesses them. This means database can’t have exclusive access and the operations which required this access throws an error. There is very easy method to overcome this minor issue – a single line script can give you exclusive access to the database. Difference between DATETIME and DATETIME2 Developers have found the root reason of the problem when dealing with Date Functions – when data time values are converted (implicit or explicit) between different data types, which would lose some precision, so the result cannot match each other as expected. In this blog post I go over very interesting details and difference between DATETIME and DATETIME2 History of SQL Server Database Encryption I recently met Michael Coles and Rodeney Landrum the author of one of the kind book Expert SQL Server 2008 Encryption at SQLPASS in Seattle. During the conversation we ended up how Microsoft is evolving encryption technology. The same discussion lead to talking about history of encryption tools in SQL Server. Michale pointed me to page 18 of his book of encryption. He explicitly gave me permission to re-produce relevant part of history from his book. 2011 Functions FIRST_VALUE and LAST_VALUE with OVER clause and ORDER BY Some time an interesting feature and smart audience make a total difference in places. From last two days, I have been writing on SQL Server 2012 feature FIRST_VALUE and LAST_VALUE. I created a puzzle which was very interesting and got many people attempt to resolve it. It was based on following two articles: Introduction to FIRST_VALUE and LAST_VALUE Introduction to FIRST_VALUE and LAST_VALUE with OVER clause I even provided the hint about how one can solve this problem. The best part was many people solved the problem without using hints! Try your luck!  A Real Story of Book Getting ‘Out of Stock’ to A 25% Discount Story Available This is a great problem and everybody would love to have it. We had it and we loved it. Our book got out of stock in 48 hours of releasing and stocks were empty. We faced many issues and learned many valuable lessons. Some we were able to avoid in the future and some we are still facing it as those problems have no solutions. However, since that day – our books never gone out of stock. This inspiring learning story for us and I am confident that you will love to read it as well. Introduction to LEAD and LAG – Analytic Functions Introduced in SQL Server 2012 SQL Server 2012 introduces new analytical function LEAD() and LAG(). This function accesses data from a subsequent row (for lead) and previous row (for lag) in the same result set without the use of a self-join . It will be very difficult to explain this in words so I will attempt small example to explain you this function. I had a fantastic time writing this blog post and I am very confident when you read it, you will like the same. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Weekly Series – Memory Lane – #038

  - by Pinal Dave

  Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 CASE Statement in ORDER BY Clause – ORDER BY using Variable This article is as per request from the Application Development Team Leader of my company. His team encountered code where the application was preparing string for ORDER BY clause of the SELECT statement. Application was passing this string as variable to Stored Procedure (SP) and SP was using EXEC to execute the SQL string. This is not good for performance as Stored Procedure has to recompile every time due to EXEC. sp_executesql can do the same task but still not the best performance. SSMS – View/Send Query Results to Text/Grid/Files Results to Text – CTRL + T Results to Grid – CTRL + D Results to File – CTRL + SHIFT + F 2008 Introduction to SPARSE Columns Part 2 I wrote about Introduction to SPARSE Columns Part 1. Let us understand the concept of the SPARSE column in more detail. I suggest you read the first part before continuing reading this article. All SPARSE columns are stored as one XML column in the database. Let us see some of the advantage and disadvantage of SPARSE column. Deferred Name Resolution How come when table name is incorrect SP can be created successfully but when an incorrect column is used SP cannot be created? 2009 Backup Timeline and Understanding of Database Restore Process in Full Recovery Model In general, databases backup in full recovery mode is taken in three different kinds of database files. Full Database Backup Differential Database Backup Log Backup Restore Sequence and Understanding NORECOVERY and RECOVERY While doing RESTORE Operation if you restoring database files, always use NORECOVER option as that will keep the database in a state where more backup file are restored. This will also keep database offline also to prevent any changes, which can create itegrity issues. Once all backup file is restored run RESTORE command with a RECOVERY option to get database online and operational. Four Different Ways to Find Recovery Model for Database Perhaps, the best thing about technical domain is that most of the things can be executed in more than one ways. It is always useful to know about the various methods of performing a single task. Two Methods to Retrieve List of Primary Keys and Foreign Keys of Database When Information Schema is used, we will not be able to discern between primary key and foreign key; we will have both the keys together. In the case of sys schema, we can query the data in our preferred way and can join this table to another table, which can retrieve additional data from the same. Get Last Running Query Based on SPID PID is returns sessions ID of the current user process. The acronym SPID comes from the name of its earlier version, Server Process ID. 2010 SELECT * FROM dual – Dual Equivalent Dual is a table that is created by Oracle together with data dictionary. It consists of exactly one column named “dummy”, and one record. The value of that record is X. You can check the content of the DUAL table using the following syntax. SELECT * FROM dual Identifying Statistics Used by Query Someone asked this question in my training class of query optimization and performance tuning.  “Can I know which statistics were used by my query?” 2011 SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 14 of 31 What are the basic functions for master, msdb, model, tempdb and resource databases? What is the Maximum Number of Index per Table? Explain Few of the New Features of SQL Server 2008 Management Studio Explain IntelliSense for Query Editing Explain MultiServer Query Explain Query Editor Regions Explain Object Explorer Enhancements Explain Activity Monitors SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 15 of 31 What is Service Broker? Where are SQL server Usernames and Passwords Stored in the SQL server? What is Policy Management? What is Database Mirroring? What are Sparse Columns? What does TOP Operator Do? What is CTE? What is MERGE Statement? What is Filtered Index? Which are the New Data Types Introduced in SQL SERVER 2008? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 16 of 31 What are the Advantages of Using CTE? How can we Rewrite Sub-Queries into Simple Select Statements or with Joins? What is CLR? What are Synonyms? What is LINQ? What are Isolation Levels? What is Use of EXCEPT Clause? What is XPath? What is NOLOCK? What is the Difference between Update Lock and Exclusive Lock? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 17 of 31 How will you Handle Error in SQL SERVER 2008? What is RAISEERROR? What is RAISEERROR? How to Rebuild the Master Database? What is the XML Datatype? What is Data Compression? What is Use of DBCC Commands? How to Copy the Tables, Schema and Views from one SQL Server to Another? How to Find Tables without Indexes? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 18 of 31 How to Copy Data from One Table to Another Table? What is Catalog Views? What is PIVOT and UNPIVOT? What is a Filestream? What is SQLCMD? What do you mean by TABLESAMPLE? What is ROW_NUMBER()? What are Ranking Functions? What is Change Data Capture (CDC) in SQL Server 2008? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 19 of 31 How can I Track the Changes or Identify the Latest Insert-Update-Delete from a Table? What is the CPU Pressure? How can I Get Data from a Database on Another Server? What is the Bookmark Lookup and RID Lookup? What is Difference between ROLLBACK IMMEDIATE and WITH NO_WAIT during ALTER DATABASE? What is Difference between GETDATE and SYSDATETIME in SQL Server 2008? How can I Check that whether Automatic Statistic Update is Enabled or not? How to Find Index Size for Each Index on Table? What is the Difference between Seek Predicate and Predicate? What are Basics of Policy Management? What are the Advantages of Policy Management? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 20 of 31 What are Policy Management Terms? What is the ‘FILLFACTOR’? Where in MS SQL Server is ’100’ equal to ‘0’? What are Points to Remember while Using the FILLFACTOR Argument? What is a ROLLUP Clause? What are Various Limitations of the Views? What is a Covered index? When I Delete any Data from a Table, does the SQL Server reduce the size of that table? What are Wait Types? How to Stop Log File Growing too Big? If any Stored Procedure is Encrypted, then can we see its definition in Activity Monitor? 2012 Example of Width Sensitive and Width Insensitive Collation Width Sensitive Collation: A single-byte character (half-width) represented as single-byte and the same character represented as a double-byte character (full-width) are when compared are not equal the collation is width sensitive. In this example we have one table with two columns. One column has a collation of width sensitive and the second column has a collation of width insensitive. Find Column Used in Stored Procedure – Search Stored Procedure for Column Name Very interesting conversation about how to find column used in a stored procedure. There are two different characters in the story and both are having a conversation about how to find column in the stored procedure. Here are two part story Part 1 | Part 2 SQL SERVER – 2012 Functions – FORMAT() and CONCAT() – An Interesting Usage Generate Script for Schema and Data – SQL in Sixty Seconds #021 – Video In simple words, in many cases the database move from one place to another place. It is not always possible to back up and restore databases. There are possibilities when only part of the database (with schema and data) has to be moved. In this video we learn that we can easily generate script for schema for data and move from one server to another one. INFORMATION_SCHEMA.COLUMNS and Value Character Maximum Length -1 I often see the value -1 in the CHARACTER_MAXIMUM_LENGTH column of INFORMATION_SCHEMA.COLUMNS table. I understand that the length of any column can be between 0 to large number but I do not get it when I see value in negative (i.e. -1). Any insight on this subject? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Weekly Series – Memory Lane – #049

  - by Pinal Dave

  Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 Two Connections Related Global Variables Explained – @@CONNECTIONS and @@MAX_CONNECTIONS @@CONNECTIONS Returns the number of attempted connections, either successful or unsuccessful since SQL Server was last started. @@MAX_CONNECTIONS Returns the maximum number of simultaneous user connections allowed on an instance of SQL Server. The number returned is not necessarily the number currently configured. Query Editor – Microsoft SQL Server Management Studio This post may be very simple for most of the users of SQL Server 2005. Earlier this year, I have received one question many times – Where is Query Analyzer in SQL Server 2005? I wrote small post about it and pointed many users to that post – SQL SERVER – 2005 Query Analyzer – Microsoft SQL SERVER Management Studio. Recently I have been receiving similar question. OUTPUT Clause Example and Explanation with INSERT, UPDATE, DELETE SQL Server 2005 has a new OUTPUT clause, which is quite useful. OUTPUT clause has access to insert and deleted tables (virtual tables) just like triggers. OUTPUT clause can be used to return values to client clause. OUTPUT clause can be used with INSERT, UPDATE, or DELETE to identify the actual rows affected by these statements. OUTPUT clause can generate a table variable, a permanent table, or temporary table. Even though, @@Identity will still work with SQL Server 2005, however I find the OUTPUT clause very easy and powerful to use. Let us understand the OUTPUT clause using an example. Find Name of The SQL Server Instance Based on database server stored procedures has to run different logic. We came up with two different solutions. 1) When database schema is very much changed, we wrote completely new stored procedure and deprecated older version once it was not needed. 2) When logic depended on Server Name we used global variable @@SERVERNAME. It was very convenient while writing migrating script which depended on the server name for the same database. Explanation of TRY…CATCH and ERROR Handling With RAISEERROR Function One of the developers at my company thought that we can not use the RAISEERROR function in new feature of SQL Server 2005 TRY… CATCH. When asked for an explanation he suggested SQL SERVER – 2005 Explanation of TRY… CATCH and ERROR Handling article as excuse suggesting that I did not give example of RAISEERROR with TRY…CATCH. We all thought it was funny. Just to keep records straight, TRY… CATCH can sure use RAISEERROR function. Different Types of Cache Objects Serveral kinds of objects can be stored in the procedure cache: Compiled Plans: When the query optimizer finishes compiling a query plan, the principal output is compiled plan. Execution contexts: While executing a compiled plan, SQL Server has to keep track of information about the state of execution. Cursors: Cursors track the execution state of server-side cursors, including the cursor’s current location within a resultset. Algebrizer trees: The Algebrizer’s job is to produce an algebrizer tree, which represents the logic structure of a query. Open SSMS From Command Prompt – sqlwb.exe Example This article is written by request and suggestion of Sr. Web Developer at my organization. Due to the nature of this article most of the content is referred from Book On-Line. sqlwbcommand prompt utility which opens SQL Server Management Studio. Squib command does not run queries from the command prompt. sqlcmd utility runs queries from command prompt, read for more information. 2008 Puzzle – Solution – Computed Columns Datatype Explanation Just a day before I wrote article SQL SERVER – Puzzle – Computed Columns Datatype Explanation which was inspired by SQL Server MVP Jacob Sebastian. I suggest that before continuing this article read the original puzzle question SQL SERVER – Puzzle – Computed Columns Datatype Explanation.The question was if the computed column was of datatype TINYINT how to create a Computed Column of datatype INT? 2008 – Find If Index is Being Used in Database It is very often I get a query that how to find if any index is being used in the database or not. If any database has many indexes and not all indexes are used it can adversely affect performance. If the number of indices are higher it reduces the INSERT / UPDATE / DELETE operation but increase the SELECT operation. It is recommended to drop any unused indexes from table to improve the performance. 2009 Interesting Observation – Execution Plan and Results of Aggregate Concatenation Queries If you want to see what’s going on here, I think you need to shift your point of view from an implementation-centric view to an ANSI point of view. ANSI does not guarantee processing the order. Figure 2 is interesting, but it will be potentially misleading if you don’t understand the ANSI rule-set SQL Server operates under in most cases. Implementation thinking can certainly be useful at times when you really need that multi-million row query to finish before the backup fire off, but in this case, it’s counterproductive to understanding what is going on. SQL Server Management Studio and Client Statistics Client Statistics are very important. Many a times, people relate queries execution plan to query cost. This is not a good comparison. Both parameters are different, and they are not always related. It is possible that the query cost of any statement is less, but the amount of the data returned is considerably larger, which is causing any query to run slow. How do we know if any query is retrieving a large amount data or very little data? 2010 I encourage all of you to go through complete series and write your own on the subject. If you write an article and send it to me, I will publish it on this blog with due credit to you. If you write on your own blog, I will update this blog post pointing to your blog post. SQL SERVER – ORDER BY Does Not Work – Limitation of the View 1 SQL SERVER – Adding Column is Expensive by Joining Table Outside View – Limitation of the View 2 SQL SERVER – Index Created on View not Used Often – Limitation of the View 3 SQL SERVER – SELECT * and Adding Column Issue in View – Limitation of the View 4 SQL SERVER – COUNT(*) Not Allowed but COUNT_BIG(*) Allowed – Limitation of the View 5 SQL SERVER – UNION Not Allowed but OR Allowed in Index View – Limitation of the View 6 SQL SERVER – Cross Database Queries Not Allowed in Indexed View – Limitation of the View 7 SQL SERVER – Outer Join Not Allowed in Indexed Views – Limitation of the View 8 SQL SERVER – SELF JOIN Not Allowed in Indexed View – Limitation of the View 9 SQL SERVER – Keywords View Definition Must Not Contain for Indexed View – Limitation of the View 10 SQL SERVER – View Over the View Not Possible with Index View – Limitations of the View 11 SQL SERVER – Get Query Running in Session I was recently looking for syntax where I needed a query running in any particular session. I always remembered the syntax and ha d actually written it down before, but somehow it was not coming to mind quickly this time. I searched online and I ended up on my own article written last year SQL SERVER – Get Last Running Query Based on SPID. I felt that I am getting old because I forgot this really simple syntax. Find Total Number of Transaction on Interval In one of my recent Performance Tuning assignments I was asked how do someone know how many transactions are happening on a server during certain interval. I had a handy script for the same. Following script displays transactions happened on the server at the interval of one minute. You can change the WAITFOR DELAY to any other interval and it should work. 2011 Here are two DMV’s which are newly introduced in SQL Server 2012 and provides vital information about SQL Server. DMV – sys.dm_os_volume_stats – Information about operating system volume DMV – sys.dm_os_windows_info – Information about Operating System SQL Backup and FTP – A Quick and Handy Tool I have used this tool extensively since 2009 at numerous occasion and found it to be very impressive. What separates it from the crowd the most – it is it’s apparent simplicity and speed. When I install SQLBackupAndFTP and configure backups – all in 1 or 2 minutes, my clients are always impressed. Quick Note about JOIN – Common Questions and Simple Answers In this blog post we are going to talk about join and lots of things related to the JOIN. I recently started office hours to answer questions and issues of the community. I receive so many questions that are related to JOIN. I will share a few of the same over here. Most of them are basic, but note that the basics are of great importance. 2012 Importance of User Without Login Question: “In recent version of SQL Server we can create user without login. What is the use of it?” Great question indeed. Let me first attempt to answer this question but after reading my answer I need your help. I want you to help him as well with adding more value to it. Preserve Leading Zero While Coping to Excel from SSMS Earlier I wrote two articles about how to efficiently copy data from SSMS to Excel. Since I wrote that post there are plenty of interest generated on this subject. There are a few questions I keep on getting over this subject. One of the question is how to get the leading zero preserved while copying the data from SSMS to Excel. Well it is almost the same way as my earlier post SQL SERVER – Excel Losing Decimal Values When Value Pasted from SSMS ResultSet. The key here is in EXCEL and not in SQL Server. Solution – 2 T-SQL Puzzles – Display Star and Shortest Code to Display 1 Earlier on this blog we had asked two puzzles. The response from all of you is nothing but Amazing. I have received 350+ responses. Many are valid and many were indeed something I had not thought about it. I strongly suggest you read all the puzzles and their answers here - trust me if you start reading the comments you will not stop till you read every single comment. Seriously trust me on it. Personally I have learned a lot from it. Identify Most Resource Intensive Queries – SQL in Sixty Seconds #028 – Video http://www.youtube.com/watch?v=TvlYy-TGaaA Importance of User Without Login – T-SQL Demo Script Earlier I wrote a blog post about SQL SERVER – Importance of User Without Login and my friend and SQL Expert Vinod Kumar has written excellent follow up blog post about Contained Databases inside SQL Server 2012. Now lots of people asked me if I can also explain the same concept again so here is the small demonstration for it. Let me show you how login without user can help. Before we continue on this subject I strongly recommend that you read my earlier blog post here. In following demo I am going to demonstrate following situation. Login using the System Admin account Create a user without login Checking Access Impersonate the user without login Checking Access Revert Impersonation Give Permission to user without login Impersonate the user without login Checking Access Revert Impersonation Clean up Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Weekly Series – Memory Lane – #039

  - by Pinal Dave

  Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 FQL – Facebook Query Language Facebook list following advantages of FQL: Condensed XML reduces bandwidth and parsing costs. More complex requests can reduce the number of requests necessary. Provides a single consistent, unified interface for all of your data. It’s fun! UDF – Get the Day of the Week Function The day of the week can be retrieved in SQL Server by using the DatePart function. The value returned by the function is between 1 (Sunday) and 7 (Saturday). To convert this to a string representing the day of the week, use a CASE statement. UDF – Function to Get Previous And Next Work Day – Exclude Saturday and Sunday While reading ColdFusion blog of Ben Nadel Getting the Previous Day In ColdFusion, Excluding Saturday And Sunday, I realize that I use similar function on my SQL Server Database. This function excludes the Weekends (Saturday and Sunday), and it gets previous as well as next work day. Complete Series of SQL Server Interview Questions and Answers Data Warehousing Interview Questions and Answers – Introduction Data Warehousing Interview Questions and Answers – Part 1 Data Warehousing Interview Questions and Answers – Part 2 Data Warehousing Interview Questions and Answers – Part 3 Data Warehousing Interview Questions and Answers Complete List Download 2008 Introduction to Log Viewer In SQL Server all the windows event logs can be seen along with SQL Server logs. Interface for all the logs is same and can be launched from the same place. This log can be exported and filtered as well. DBCC SHRINKFILE Takes Long Time to Run If you are DBA who are involved with Database Maintenance and file group maintenance, you must have experience that many times DBCC SHRINKFILE operations takes a long time but any other operations with Database are relatively quicker. mssqlsystemresource – Resource Database The purpose of resource database is to facilitates upgrading to the new version of SQL Server without any hassle. In previous versions whenever version of SQL Server was upgraded all the previous version system objects needs to be dropped and new version system objects to be created. 2009 Puzzle – Write Script to Generate Primary Key and Foreign Key In SQL Server Management Studio (SSMS), there is no option to script all the keys. If one is required to script keys they will have to manually script each key one at a time. If database has many tables, generating one key at a time can be a very intricate task. I want to throw a question to all of you if any of you have scripts for the same purpose. Maximizing View of SQL Server Management Studio – Full Screen – New Screen I had explained the following two different methods: 1) Open Results in Separate Tab - This is a very interesting method as result pan shows up in a different tab instead of the splitting screen horizontally. 2) Open SSMS in Full Screen - This works always and to its best. Not many people are aware of this method; hence, very few people use it to enhance performance. 2010 Find Queries using Parallelism from Cached Plan T-SQL script gets all the queries and their execution plan where parallelism operations are kicked up. Pay attention there is TOP 10 is used, if you have lots of transactional operations, I suggest that you change TOP 10 to TOP 50 This is the list of the all the articles in the series of computed columns. SQL SERVER – Computed Column – PERSISTED and Storage This article talks about how computed columns are created and why they take more storage space than before. SQL SERVER – Computed Column – PERSISTED and Performance This article talks about how PERSISTED columns give better performance than non-persisted columns. SQL SERVER – Computed Column – PERSISTED and Performance – Part 2 This article talks about how non-persisted columns give better performance than PERSISTED columns. SQL SERVER – Computed Column and Performance – Part 3 This article talks about how Index improves the performance of Computed Columns. SQL SERVER – Computed Column – PERSISTED and Storage – Part 2 This article talks about how creating index on computed column does not grow the row length of table. SQL SERVER – Computed Columns – Index and Performance This article summarized all the articles related to computed columns. 2011 SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Data Warehousing Concepts – Day 21 of 31 What is Data Warehousing? What is Business Intelligence (BI)? What is a Dimension Table? What is Dimensional Modeling? What is a Fact Table? What are the Fundamental Stages of Data Warehousing? What are the Different Methods of Loading Dimension tables? Describes the Foreign Key Columns in Fact Table and Dimension Table? What is Data Mining? What is the Difference between a View and a Materialized View? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Data Warehousing Concepts – Day 22 of 31 What is OLTP? What is OLAP? What is the Difference between OLTP and OLAP? What is ODS? What is ER Diagram? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Data Warehousing Concepts – Day 23 of 31 What is ETL? What is VLDB? Is OLTP Database is Design Optimal for Data Warehouse? If denormalizing improves Data Warehouse Processes, then why is the Fact Table is in the Normal Form? What are Lookup Tables? What are Aggregate Tables? What is Real-Time Data-Warehousing? What are Conformed Dimensions? What is a Conformed Fact? How do you Load the Time Dimension? What is a Level of Granularity of a Fact Table? What are Non-Additive Facts? What is a Factless Facts Table? What are Slowly Changing Dimensions (SCD)? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Data Warehousing Concepts – Day 24 of 31 What is Hybrid Slowly Changing Dimension? What is BUS Schema? What is a Star Schema? What Snow Flake Schema? Differences between the Star and Snowflake Schema? What is Difference between ER Modeling and Dimensional Modeling? What is Degenerate Dimension Table? Why is Data Modeling Important? What is a Surrogate Key? What is Junk Dimension? What is a Data Mart? What is the Difference between OLAP and Data Warehouse? What is a Cube and Linked Cube with Reference to Data Warehouse? What is Snapshot with Reference to Data Warehouse? What is Active Data Warehousing? What is the Difference between Data Warehousing and Business Intelligence? What is MDS? Explain the Paradigm of Bill Inmon and Ralph Kimball. SQL SERVER – Azure Interview Questions and Answers – Guest Post by Paras Doshi – Day 25 of 31 Paras Doshi has submitted 21 interesting question and answers for SQL Azure. 1.What is SQL Azure? 2.What is cloud computing? 3.How is SQL Azure different than SQL server? 4.How many replicas are maintained for each SQL Azure database? 5.How can we migrate from SQL server to SQL Azure? 6.Which tools are available to manage SQL Azure databases and servers? 7.Tell me something about security and SQL Azure. 8.What is SQL Azure Firewall? 9.What is the difference between web edition and business edition? 10.How do we synchronize On Premise SQL server with SQL Azure? 11.How do we Backup SQL Azure Data? 12.What is the current pricing model of SQL Azure? 13.What is the current limitation of the size of SQL Azure DB? 14.How do you handle datasets larger than 50 GB? 15.What happens when the SQL Azure database reaches Max Size? 16.How many databases can we create in a single server? 17.How many servers can we create in a single subscription? 18.How do you improve the performance of a SQL Azure Database? 19.What is code near application topology? 20.What were the latest updates to SQL Azure service? 21.When does a workload on SQL Azure get throttled? SQL SERVER – Interview Questions and Answers – Guest Post by Malathi Mahadevan – Day 26 of 31 Malachi had asked a simple question which has several answers. Each answer makes you think and ponder about the reality of the IT world. Look at the simple question – ‘What is the toughest challenge you have faced in your present job and how did you handle it’? and its various answers. Each answer has its own story. SQL SERVER – Interview Questions and Answers – Guest Post by Rick Morelan – Day 27 of 31 Rick Morelan of Joes2Pros has written an excellent blog post on the subject how to find top N values. Most people are fully aware of how the TOP keyword works with a SELECT statement. After years preparing so many students to pass the SQL Certification I noticed they were pretty well prepared for job interviews too. Yes, they would do well in the interview but not great. There seemed to be a few questions that would come up repeatedly for almost everyone. Rick addresses similar questions in his lucid writing skills. 2012 Observation of Top with Index and Order of Resultset SQL Server has lots of things to learn and share. It is amazing to see how people evaluate and understand different techniques and styles differently when implementing. The real reason may be absolutely different but we may blame something totally different for the incorrect results. Read the blog post to learn more. How do I Record Video and Webcast How to Convert Hex to Decimal or INT Earlier I asked regarding a question about how to convert Hex to Decimal. I promised that I will post an answer with Due Credit to the author but never got around to post a blog post around it. Read the original post over here SQL SERVER – Question – How to Convert Hex to Decimal. Query to Get Unique Distinct Data Based on Condition – Eliminate Duplicate Data from Resultset The natural reaction will be to suggest DISTINCT or GROUP BY. However, not all the questions can be solved by DISTINCT or GROUP BY. Let us see the following example, where a user wanted only latest records to be displayed. Let us see the example to understand further. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Weekly Series – Memory Lane – #037

  - by Pinal Dave

  Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 Convert Text to Numbers (Integer) – CAST and CONVERT If table column is VARCHAR and has all the numeric values in it, it can be retrieved as Integer using CAST or CONVERT function. List All Stored Procedure Modified in Last N Days If SQL Server suddenly start behaving in un-expectable behavior and if stored procedure were changed recently, following script can be used to check recently modified stored procedure. If a stored procedure was created but never modified afterwards modified date and create a date for that stored procedure are same. Count Duplicate Records – Rows Validate Field For DATE datatype using function ISDATE() We always checked DATETIME field for incorrect data type. One of the user input date as 30/2/2007. The date was sucessfully inserted in the temp table but while inserting from temp table to final table it crashed with error. We had now task to validate incorrect date value before we insert in final table. Jr. Developer asked me how can he do that? We check for incorrect data type (varchar, int, NULL) but this is incorrect date value. Regular expression works fine with them because of mm/dd/yyyy format. 2008 Find Space Used For Any Particular Table It is very simple to find out the space used by any table in the database. Two Convenient Features Inline Assignment – Inline Operations Here is the script which does both – Inline Assignment and Inline Operation DECLARE @idx INT = 0 SET @idx+=1 SELECT @idx Introduction to SPARSE Columns SPARSE column are better at managing NULL and ZERO values in SQL Server. It does not take any space in database at all. If column is created with SPARSE clause with it and it contains ZERO or NULL it will be take lesser space then regular column (without SPARSE clause). SP_CONFIGURE – Displays or Changes Global Configuration Settings If advanced settings are not enabled at configuration level SQL Server will not let user change the advanced features on server. Authorized user can turn on or turn off advance settings. 2009 Standby Servers and Types of Standby Servers Standby Server is a type of server that can be brought online in a situation when Primary Server goes offline and application needs continuous (high) availability of the server. There is always a need to set up a mechanism where data and objects from primary server are moved to secondary (standby) server. BLOB – Pointer to Image, Image in Database, FILESTREAM Storage When it comes to storing images in database there are two common methods. I had previously blogged about the same subject on my visit to Toronto. With SQL Server 2008, we have a new method of FILESTREAM storage. However, the answer on when to use FILESTREAM and when to use other methods is still vague in community. 2010 Upper Case Shortcut SQL Server Management Studio I select the word and hit CTRL+SHIFT+U and it SSMS immediately changes the case of the selected word. Similar way if one want to convert cases to lower case, another short cut CTRL+SHIFT+L is also available. The Self Join – Inner Join and Outer Join Self Join has always been a noteworthy case. It is interesting to ask questions about self join in a room full of developers. I often ask – if there are three kinds of joins, i.e.- Inner Join, Outer Join and Cross Join; what type of join is Self Join? The usual answer is that it is an Inner Join. However, the reality is very different. Parallelism – Row per Processor – Row per Thread – Thread 0  If you look carefully in the Properties window or XML Plan, there is “Thread 0?. What does this “Thread 0” indicate? Well find out from the blog post. How do I Learn and How do I Teach The blog post has raised three very interesting questions. How do you learn? How do you teach? What are you learning or teaching? Let me try to answer the same. 2011 SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 7 of 31 What are Different Types of Locks? What are Pessimistic Lock and Optimistic Lock? When is the use of UPDATE_STATISTICS command? What is the Difference between a HAVING clause and a WHERE clause? What is Connection Pooling and why it is Used? What are the Properties and Different Types of Sub-Queries? What are the Authentication Modes in SQL Server? How can it be Changed? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 8 of 31 Which Command using Query Analyzer will give you the Version of SQL Server and Operating System? What is an SQL Server Agent? Can a Stored Procedure call itself or a Recursive Stored Procedure? How many levels of SP nesting is possible? What is Log Shipping? Name 3 ways to get an Accurate Count of the Number of Records in a Table? What does it mean to have QUOTED_IDENTIFIER ON? What are the Implications of having it OFF? What is the Difference between a Local and a Global Temporary Table? What is the STUFF Function and How Does it Differ from the REPLACE Function? What is PRIMARY KEY? What is UNIQUE KEY Constraint? What is FOREIGN KEY? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 9 of 31 What is CHECK Constraint? What is NOT NULL Constraint? What is the difference between UNION and UNION ALL? What is B-Tree? How to get @@ERROR and @@ROWCOUNT at the Same Time? What is a Scheduled Job or What is a Scheduled Task? What are the Advantages of Using Stored Procedures? What is a Table Called, if it has neither Cluster nor Non-cluster Index? What is it Used for? Can SQL Servers Linked to other Servers like Oracle? What is BCP? When is it Used? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 10 of 31 What Command do we Use to Rename a db, a Table and a Column? What are sp_configure Commands and SET Commands? How to Implement One-to-One, One-to-Many and Many-to-Many Relationships while Designing Tables? What is Difference between Commit and Rollback when Used in Transactions? What is an Execution Plan? When would you Use it? How would you View the Execution Plan? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 11 of 31 What is Difference between Table Aliases and Column Aliases? Do they Affect Performance? What is the difference between CHAR and VARCHAR Datatypes? What is the Difference between VARCHAR and VARCHAR(MAX) Datatypes? What is the Difference between VARCHAR and NVARCHAR datatypes? Which are the Important Points to Note when Multilanguage Data is Stored in a Table? How to Optimize Stored Procedure Optimization? What is SQL Injection? How to Protect Against SQL Injection Attack? How to Find Out the List Schema Name and Table Name for the Database? What is CHECKPOINT Process in the SQL Server? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 12 of 31 How does Using a Separate Hard Drive for Several Database Objects Improves Performance Right Away? How to Find the List of Fixed Hard Drive and Free Space on Server? Why can there be only one Clustered Index and not more than one? What is Difference between Line Feed (\n) and Carriage Return (\r)? Is It Possible to have Clustered Index on Separate Drive From Original Table Location? What is a Hint? How to Delete Duplicate Rows? Why the Trigger Fires Multiple Times in Single Login? 2012 CTRL+SHIFT+] Shortcut to Select Code Between Two Parenthesis Shortcut key is CTRL+SHIFT+]. This key can be very useful when dealing with multiple subqueries, CTE or query with multiple parentheses. When exercised this shortcut key it selects T-SQL code between two parentheses. Monday Morning Puzzle – Query Returns Results Sometimes but Not Always I am beginner with SQL Server. I have one query, it sometime returns a result and sometime it does not return me the result. Where should I start looking for a solution and what kind of information I should send to you so you can help me with solving. I have no clue, please guide me. Remove Debug Button in SSMS – SQL in Sixty Seconds #020 – Video Effect of Case Sensitive Collation on Resultset Collation is a very interesting concept but I quite often see it is heavily neglected. I have seen developer and DBA looking for a workaround to fix collation error rather than understanding if the side effect of the workaround. Switch Between Two Parenthesis using Shortcut CTRL+] Earlier this week I wrote a blog post about CTRL+SHIFT+] Shortcut to Select Code Between Two Parenthesis, I received quite a lot of positive feedback from readers. If you are a regular reader of the blog post, you must be aware that I appreciate the learning shared by readers. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Weekly Series – Memory Lane – #007

  - by pinaldave

  Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2006 Find Stored Procedure Related to Table in Database – Search in All Stored Procedure In 2006 I wrote a small script which will help user  find all the Stored Procedures (SP) which are related to one or more specific tables. This was quite a popular script however, in SQL Server 2012 the same can be achieved using new DMV sys.sql-expression_dependencies. I recently blogged about it over Find Referenced or Referencing Object in SQL Server using sys.sql_expression_dependencies. 2007 SQL SERVER – Versions, CodeNames, Year of Release 1993 – SQL Server 4.21 for Windows NT 1995 – SQL Server 6.0, codenamed SQL95 1996 – SQL Server 6.5, codenamed Hydra 1999 – SQL Server 7.0, codenamed Sphinx 1999 – SQL Server 7.0 OLAP, codenamed Plato 2000 – SQL Server 2000 32-bit, codenamed Shiloh (version 8.0) 2003 – SQL Server 2000 64-bit, codenamed Liberty 2005 – SQL Server 2005, codenamed Yukon (version 9.0) 2008 – SQL Server 2008, codenamed Katmai (version 10.0) 2011 – SQL Server 2008, codenamed Denali (version 11.0) Search String in Stored Procedure Searching sting in the stored procedure is one of the most frequent task developer do. They might be searching for a table, view or any other details. I have written a script to do the same in SQL Server 2000 and SQL Server 2005. This is worth bookmarking blog post. There is an alternative way to do the same as well here is the example. 2008 SQL SERVER – Refresh Database Using T-SQL NO! Some of the questions have a single answer NO! You may want to read the question in the original blog post. I had a great time saying No! SQL SERVER – Delete Backup History – Cleanup Backup History SQL Server stores history of all the taken backup forever. History of all the backup is stored in the msdb database. Many times older history is no more required. Following Stored Procedure can be executed with a parameter which takes days of history to keep. In the following example 30 is passed to keep a history of month. 2009 Stored Procedure are Compiled on First Run – SP taking Longer to Run First Time Is stored procedure pre-compiled? Why the Stored Procedure takes a long time to run for the first time?  This is a very common questions often discussed by developers and DBAs. There is an absolutely definite answer but the question has been discussed forever. There is a misconception that stored procedures are pre-compiled. They are not pre-compiled, but compiled only during the first run. For every subsequent runs, it is for sure pre-compiled. Read the entire article for example and demonstration. Removing Key Lookup – Seek Predicate – Predicate – An Interesting Observation Related to Datatypes This is one of the most important performance tuning lesson on my blog. I suggest this weekend you spend time reading them and let me know what you think about the concepts which I have demonstrated in the four part series. Part 1 | Part 2 | Part 3 | Part 4 Seek Predicate is the operation that describes the b-tree portion of the Seek. Predicate is the operation that describes the additional filter using non-key columns. Based on the description, it is very clear that Seek Predicate is better than Predicate as it searches indexes whereas in Predicate, the search is on non-key columns – which implies that the search is on the data in page files itself. Policy Based Management – Create, Evaluate and Fix Policies This article will cover the most spectacular feature of SQL Server – Policy-based management and how the configuration of SQL Server with policy-based management architecture can make a powerful difference. Policy based management is loaded with several advantages. It can help you implement various policies for reliable configuration of the system. It also provides additional administration assistance to DBAs and helps them effortlessly manage various tasks of SQL Server across the enterprise. 2010 Recycle Error Log – Create New Log file without Server Restart Once I observed a DBA to restaring the SQL Server when he needed new error log file. This was funny and sad both at the same time. There is no need to restart the server to create a new log file or recycle the log file. You can run sp_cycle_errorlog and achieve the same result. Get Database Backup History for a Single Database Simple but effective script! Reducing CXPACKET Wait Stats for High Transactional Database The subject is very complex and I have done my best to simplify the concept. In simpler words, when a parallel operation is created for SQL Query, there are multiple threads for a single query. Each query deals with a different set of the data (or rows). Due to some reasons, one or more of the threads lag behind, creating the CXPACKET Wait Stat. Threads which came first have to wait for the slower thread to finish. The Wait by a specific completed thread is called CXPACKET Wait Stat. Information Related to DATETIME and DATETIME2 There are quite a lot of confusion with DATETIME and DATETIME2. DATETIME2 is also one of the underutilized datatype of SQL Server.  In this blog post I have written a follow up of the my earlier datetime series where I clarify a few of the concepts related to datetime. Difference Between GETDATE and SYSDATETIME Difference Between DATETIME and DATETIME2 – WITH GETDATE Difference Between DATETIME and DATETIME2 2011 Introduction to CUME_DIST – Analytic Functions Introduced in SQL Server 2012 SQL Server 2012 introduces new analytical function CUME_DIST(). This function provides cumulative distribution value. It will be very difficult to explain this in words so I will attempt small example to explain you this function. Instead of creating new table, I will be using AdventureWorks sample database as most of the developer uses that for experiment. Introduction to FIRST _VALUE and LAST_VALUE – Analytic Functions Introduced in SQL Server 2012 SQL Server 2012 introduces new analytical functions FIRST_VALUE() and LAST_VALUE(). This function returns first and last value from the list. It will be very difficult to explain this in words so I’d like to attempt to explain its function through a brief example. Instead of creating a new table, I will be using the AdventureWorks sample database as most developers use that for experiment purposes. OVER clause with FIRST _VALUE and LAST_VALUE – Analytic Functions Introduced in SQL Server 2012 – ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING “Don’t you think there is bug in your first example where FIRST_VALUE is remain same but the LAST_VALUE is changing every line. I think the LAST_VALUE should be the highest value in the windows or set of result.” Puzzle – Functions FIRST_VALUE and LAST_VALUE with OVER clause and ORDER BY You can see that row number 2, 3, 4, and 5 has same SalesOrderID = 43667. The FIRST_VALUE is 78 and LAST_VALUE is 77. Now if these function was working on maximum and minimum value they should have given answer as 77 and 80 respectively instead of 78 and 77. Also the value of FIRST_VALUE is greater than LAST_VALUE 77. Why? Explain in detail. Introduction to LEAD and LAG – Analytic Functions Introduced in SQL Server 2012 SQL Server 2012 introduces new analytical function LEAD() and LAG(). This functions accesses data from a subsequent row (for lead) and previous row (for lag) in the same result set without the use of a self-join . It will be very difficult to explain this in words so I will attempt small example to explain you this function. Instead of creating new table, I will be using AdventureWorks sample database as most of the developer uses that for experiment. A Real Story of Book Getting ‘Out of Stock’ to A 25% Discount Story Available Our book was out of stock in 48 hours of it was arrived in stock! We got call from the online store with a request for more copies within 12 hours. But we had printed only as many as we had sent them. There were no extra copies. We finally talked to the printer to get more copies. However, due to festivals and holidays the copies could not be shipped to the online retailer for two days. We knew for sure that they were going to be out of the book for 48 hours. This is the story of how we overcame that situation! Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Allocating memory inside a function and returning it back

  - by user2651062

  I want to pass a pointer to my function and allocate the memory to which this pointer points. I've read in other posts that I should pass a double pointer to this function and I did so, but I keep getting segmentation fault: #include <iostream> #include <stdlib.h> using namespace std; void allocate(unsigned char** t) { *t=(unsigned char*)malloc(3*sizeof(unsigned char)); if(*t == NULL) cout<<"Allcoation failed"<<endl; else for(int m=0;m<3;m++) *(t[m])=0; } int main() { unsigned char* t; allocate(&t); cout<<t[0]<<" "<<t[1]<<endl; return 0; } the result is always this: Segmentation fault (core dumped) I don't think that there's anything missing from this code. What could be wrong?

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• Free memory outside function [migrated]

  - by Dev Bag

  Can you please help with this issue, is the below gonna leak memory or is it ok? and please let me know if there is something else that I need to pay attention to typedef struct { int len; UC * message; }pack; pack * prepare_packet_to_send(const int length,const unsigned char tag,const int numargs, ... ) { pack *layer= malloc(sizeof(pack)); va_list listp; va_start( listp, numargs ); int step = 0; layer->message = (unsigned char *) malloc(length); layer->len = length; int i = 0; int len = 0; unsigned char *source_message ; for( i = 0 ; i < numargs; i++ ) { source_message = va_arg( listp, unsigned char *); len = va_arg( listp, long); memcpy(layer->message+step, source_message, (long) len); step+=len; } va_end( listp ); return layer; } main() { pack *test = call prepare_packet_to_send(sizeof(var1)+sizeof(var2),any tag,any args) // are following two frees correct/enough? or is there something else i need to do to prevent mem leak? free(test->message); free(test); }

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• Java Animation Memory Overload [on hold]

  - by user2425429

  I need a way to reduce the memory usage of these programs while keeping the functionality. Every time I add 50 milliseconds or so to the set&display loop in AnimationTest1, it throws an out of memory error. Here is the code I have now: import java.awt.DisplayMode; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Image; import java.awt.Polygon; import java.util.ArrayList; import java.util.List; import java.util.concurrent.Executor; import java.util.concurrent.Executors; import javax.swing.ImageIcon; public class AnimationTest1 { public static void main(String args[]) { AnimationTest1 test = new AnimationTest1(); test.run(); } private static final DisplayMode POSSIBLE_MODES[] = { new DisplayMode(800, 600, 32, 0), new DisplayMode(800, 600, 24, 0), new DisplayMode(800, 600, 16, 0), new DisplayMode(640, 480, 32, 0), new DisplayMode(640, 480, 24, 0), new DisplayMode(640, 480, 16, 0) }; private static final long DEMO_TIME = 4000; private ScreenManager screen; private Image bgImage; private Animation anim; public void loadImages() { // create animation List<Polygon> polygons=new ArrayList(); int[] x=new int[]{20,4,4,20,40,56,56,40}; int[] y=new int[]{20,32,40,44,44,40,32,20}; polygons.add(new Polygon(x,y,8)); anim = new Animation(); //# of frames long startTime = System.currentTimeMillis(); long currTimer = startTime; long elapsedTime = 0; boolean animated = false; Graphics2D g = screen.getGraphics(); int width=200; int height=200; //set&display loop while (currTimer - startTime < DEMO_TIME*2) { //draw the polygons if(!animated){ for(int j=0; j<polygons.size();j++){ for(int pos=0; pos<polygons.get(j).npoints; pos++){ polygons.get(j).xpoints[pos]+=1; } } anim.setNewPolyFrame(polygons , width , height , 64); } else{ // update animation anim.update(elapsedTime); draw(g); g.dispose(); screen.update(); try{ Thread.sleep(20); } catch(InterruptedException ie){} } if(currTimer - startTime == DEMO_TIME) animated=true; elapsedTime = System.currentTimeMillis() - currTimer; currTimer += elapsedTime; } } public void run() { screen = new ScreenManager(); try { DisplayMode displayMode = screen.findFirstCompatibleMode(POSSIBLE_MODES); screen.setFullScreen(displayMode); loadImages(); } finally { screen.restoreScreen(); } } public void draw(Graphics g) { // draw background g.drawImage(bgImage, 0, 0, null); // draw image g.drawImage(anim.getImage(), 0, 0, null); } } ScreenManager: import java.awt.Color; import java.awt.DisplayMode; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.GraphicsConfiguration; import java.awt.GraphicsDevice; import java.awt.GraphicsEnvironment; import java.awt.Toolkit; import java.awt.Window; import java.awt.event.KeyListener; import java.awt.event.MouseListener; import java.awt.image.BufferStrategy; import java.awt.image.BufferedImage; import javax.swing.JFrame; import javax.swing.JPanel; public class ScreenManager extends JPanel { private GraphicsDevice device; /** Creates a new ScreenManager object. */ public ScreenManager() { GraphicsEnvironment environment=GraphicsEnvironment.getLocalGraphicsEnvironment(); device = environment.getDefaultScreenDevice(); setBackground(Color.white); } /** Returns a list of compatible display modes for the default device on the system. */ public DisplayMode[] getCompatibleDisplayModes() { return device.getDisplayModes(); } /** Returns the first compatible mode in a list of modes. Returns null if no modes are compatible. */ public DisplayMode findFirstCompatibleMode( DisplayMode modes[]) { DisplayMode goodModes[] = device.getDisplayModes(); for (int i = 0; i < modes.length; i++) { for (int j = 0; j < goodModes.length; j++) { if (displayModesMatch(modes[i], goodModes[j])) { return modes[i]; } } } return null; } /** Returns the current display mode. */ public DisplayMode getCurrentDisplayMode() { return device.getDisplayMode(); } /** Determines if two display modes "match". Two display modes match if they have the same resolution, bit depth, and refresh rate. The bit depth is ignored if one of the modes has a bit depth of DisplayMode.BIT_DEPTH_MULTI. Likewise, the refresh rate is ignored if one of the modes has a refresh rate of DisplayMode.REFRESH_RATE_UNKNOWN. */ public boolean displayModesMatch(DisplayMode mode1, DisplayMode mode2) { if (mode1.getWidth() != mode2.getWidth() || mode1.getHeight() != mode2.getHeight()) { return false; } if (mode1.getBitDepth() != DisplayMode.BIT_DEPTH_MULTI && mode2.getBitDepth() != DisplayMode.BIT_DEPTH_MULTI && mode1.getBitDepth() != mode2.getBitDepth()) { return false; } if (mode1.getRefreshRate() != DisplayMode.REFRESH_RATE_UNKNOWN && mode2.getRefreshRate() != DisplayMode.REFRESH_RATE_UNKNOWN && mode1.getRefreshRate() != mode2.getRefreshRate()) { return false; } return true; } /** Enters full screen mode and changes the display mode. If the specified display mode is null or not compatible with this device, or if the display mode cannot be changed on this system, the current display mode is used. <p> The display uses a BufferStrategy with 2 buffers. */ public void setFullScreen(DisplayMode displayMode) { JFrame frame = new JFrame(); frame.setUndecorated(true); frame.setIgnoreRepaint(true); frame.setResizable(true); device.setFullScreenWindow(frame); if (displayMode != null && device.isDisplayChangeSupported()) { try { device.setDisplayMode(displayMode); } catch (IllegalArgumentException ex) { } } frame.createBufferStrategy(2); Graphics g=frame.getGraphics(); g.setColor(Color.white); g.drawRect(0, 0, frame.WIDTH, frame.HEIGHT); frame.paintAll(g); g.setColor(Color.black); g.dispose(); } /** Gets the graphics context for the display. The ScreenManager uses double buffering, so applications must call update() to show any graphics drawn. <p> The application must dispose of the graphics object. */ public Graphics2D getGraphics() { Window window = device.getFullScreenWindow(); if (window != null) { BufferStrategy strategy = window.getBufferStrategy(); return (Graphics2D)strategy.getDrawGraphics(); } else { return null; } } /** Updates the display. */ public void update() { Window window = device.getFullScreenWindow(); if (window != null) { BufferStrategy strategy = window.getBufferStrategy(); if (!strategy.contentsLost()) { strategy.show(); } } // Sync the display on some systems. // (on Linux, this fixes event queue problems) Toolkit.getDefaultToolkit().sync(); } /** Returns the window currently used in full screen mode. Returns null if the device is not in full screen mode. */ public Window getFullScreenWindow() { return device.getFullScreenWindow(); } /** Returns the width of the window currently used in full screen mode. Returns 0 if the device is not in full screen mode. */ public int getWidth() { Window window = device.getFullScreenWindow(); if (window != null) { return window.getWidth(); } else { return 0; } } /** Returns the height of the window currently used in full screen mode. Returns 0 if the device is not in full screen mode. */ public int getHeight() { Window window = device.getFullScreenWindow(); if (window != null) { return window.getHeight(); } else { return 0; } } /** Restores the screen's display mode. */ public void restoreScreen() { Window window = device.getFullScreenWindow(); if (window != null) { window.dispose(); } device.setFullScreenWindow(null); } /** Creates an image compatible with the current display. */ public BufferedImage createCompatibleImage(int w, int h, int transparency) { Window window = device.getFullScreenWindow(); if (window != null) { GraphicsConfiguration gc = window.getGraphicsConfiguration(); return gc.createCompatibleImage(w, h, transparency); } return null; } } Animation: import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Image; import java.awt.Polygon; import java.awt.image.BufferedImage; import java.util.ArrayList; import java.util.List; /** The Animation class manages a series of images (frames) and the amount of time to display each frame. */ public class Animation { private ArrayList frames; private int currFrameIndex; private long animTime; private long totalDuration; /** Creates a new, empty Animation. */ public Animation() { frames = new ArrayList(); totalDuration = 0; start(); } /** Adds an image to the animation with the specified duration (time to display the image). */ public synchronized void addFrame(BufferedImage image, long duration){ ScreenManager s = new ScreenManager(); totalDuration += duration; frames.add(new AnimFrame(image, totalDuration)); } /** Starts the animation over from the beginning. */ public synchronized void start() { animTime = 0; currFrameIndex = 0; } /** Updates the animation's current image (frame), if necessary. */ public synchronized void update(long elapsedTime) { if (frames.size() >= 1) { animTime += elapsedTime; /*if (animTime >= totalDuration) { animTime = animTime % totalDuration; currFrameIndex = 0; }*/ while (animTime > getFrame(0).endTime) { frames.remove(0); } } } /** Gets the Animation's current image. Returns null if this animation has no images. */ public synchronized Image getImage() { if (frames.size() > 0&&!(currFrameIndex>=frames.size())) { return getFrame(currFrameIndex).image; } else{ System.out.println("There are no frames!"); System.exit(0); } return null; } private AnimFrame getFrame(int i) { return (AnimFrame)frames.get(i); } private class AnimFrame { Image image; long endTime; public AnimFrame(Image image, long endTime) { this.image = image; this.endTime = endTime; } } public void setNewPolyFrame(List<Polygon> polys,int imagewidth,int imageheight,int time){ BufferedImage image=new BufferedImage(imagewidth, imageheight, 1); Graphics g=image.getGraphics(); for(int i=0;i<polys.size();i++){ g.drawPolygon(polys.get(i)); } addFrame(image,time); g.dispose(); } }

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• Lack of Virtual Memory - confusion

  - by Wesley

  Specs ahead of time: AMD Athlon XP 2400+ @ 2.00 GHz / 1 GB PC-3200 DDR RAM / 160 GB IDE HDD / 128 MB GeForce 6200 AGP / FIC AM37 / 350W PSU / Windows XP Pro SP3 So, XP has pop-ups saying that I am low on virtual memory. However, I have a program called SmartRAM (part of Advanced SystemCare by IObit) and it displays CPU & Page File Usage and Free Physical and Virtual Memory. That program shows that I have at least 2000 MB free virtual memory on my machine when the XP pop-ups say that I'm low on virtual memory. First off, would a complete lack of virtual memory cause my computer to freeze? Secondly, how can I solve this lack of virtual memory? (A complete reformat is possible but can't be done immediately...) Thanks in advance.

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• Windows 7 using exactly HALF the installed memory

  - by Nathan Ridley

  I've taken this directly from system information: Installed Physical Memory (RAM) 4.00 GB Total Physical Memory 2.00 GB Available Physical Memory 434 MB Total Virtual Memory 5.10 GB Available Virtual Memory 1.19 GB Page File Space 3.11 GB Also the BIOS reports a full 4GB available. Note the 4gb installed, yet 2gb total. I understand that on a 32 bit operating system, you'll never get the full 4gb of ram, however typically you'll get in the range of 2.5-3.2gb of ram. I have only 2gb available! My swap file goes nuts when I do anything! Note that I have dual SLI nvidia video cards, each with 512mb of on board ram, though I have the SLI feature turned off. Anybody know why Windows might claim that I have exactly 2gb of ram total? Note: previously asked on SuperUser, but closed as "belongs on superuser" before this site opened: http://serverfault.com/questions/39603/windows-7-using-exactly-half-the-installed-memory (I still need an answer!)

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• High Memory Utilization on weblogic

  - by Anup

  My Weblogic App Server shows high Memory Utization. The application seems to perform good without any memeory issues. Now that my traffix is going to increase i am worried about the memory and have a feeling things could go bad and need to take action now and i am confused as to should i increase The JVM memory on the weblogic instances which means adding more physical memory or should i increase the number of managed instances in the cluster. Would like to understand what does having high memory utilization mean and the advantage and disadvantages of adding JVM memory and adding managed instances. Thanks

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• High Memory Utilization on weblogic

  - by Anup

  My Weblogic App Server shows high Memory Utization. The application seems to perform good without any memeory issues. Now that my traffix is going to increase i am worried about the memory and have a feeling things could go bad and need to take action now and i am confused as to should i increase The JVM memory on the weblogic instances which means adding more physical memory or should i increase the number of managed instances in the cluster. Would like to understand what does having high memory utilization mean and the advantage and disadvantages of adding JVM memory and adding managed instances. Thanks

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• Virtual machine image compatibility between VMware Server and VMware Player

  - by alexandrul

  I'm trying to minimize the number of different product versions used on my PC's both at work and at home. So far I have a mixture of: VMware Server 1.0.7 VMware Server 2.0.2 VMware Player 2.5.3 VMware Player 3.0.0 and I would love to upgrade each product family to the latest version. Since Virtual Machine Mobility Guide is marked as deprecated, can anyone point me to some fresh information about virtual machine compatibility between VMware Player and VMware Server, in order to still be able to move virtual machines back and forth between the mentioned products? Update What I'm looking for is an updated document with virtual machines hardware versions, and the VMware products that are able to use that specific hardware version, so I can know - given the products that are using a specific virtual machine - what is the maximum hardware version that I can update the virtual machine to.

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• Optimal Memory Configuration for Dell PowerEdge 1800 (Windows Server 2000 32bit)

  - by David Murdoch

  I am upgrading the memory on a Dell PowerEdge 1800 Server running Windows Server 2000 (32 bit). My Computer Properties currently reports "2,096,432 KB RAM" (4 modules @ 512MB each). Crucial.com scan reports: "Each memory slot can hold DDR2 PC2-5300 with a maximum of 2GB per slot. Maximum Memory Capacity:  12288MB Currently Installed Memory:  2GB Available Memory Slots:  2 Total Memory Slots:  6 Dual Channel Support:   No CPU Manufacturer:  GenuineIntel CPU Family:  Intel(R) Xeon(TM) CPU 2.80GHz Model 4, Stepping 1 CPU Speed:  2793 MHz Installed in pairs of modules." We will be completely replacing the old 512 MB modules. Will there be any performance difference between installing 4 modules @ 1GB vs. 2 modules @ 2GB?

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• Xinetd , vncserver memory requirement

  - by JP19

  Hi, I am installing the following on a low memory system: vnc4server xinetd xterm openbox obconf I will only occasionally be logging into the vncs for some admin work. My question is: 1) Does xinetd take memory / cpu even when vncserver is not running? If so, can I "run" xinetd on demand (how)? And if no, any idea how much memory it will take when vncserver is not running? 2) Does vncserver take substantial memory when no clients are connected? 3) Do openbox/obconf take memory when vncserver is running but no client are connected? 4) Do openbox/obconf take memory when no vncserver is running? thanks JP

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• SharePoint / SQL Server "out of memory" error

  - by aardvark

  After months of preparation, we launched a new SharePoint intranet portal today. Immediately, some users began getting a "server out of memory" error when they tried to log in. The SharePoint server appeared to be fine, but the SQL Server was reporting 100% memory use. (It has 4 GB.) We rebooted the server and have not had further memory problems, though memory usage is hovering around 60% or above. I'm not convinced that we have solved the problem; I suspect it may return Monday morning when the whole staff tries to log in again. I'm not a database guy, and I'm stumped about how to troubleshoot this. Do we need more memory, or is there somewhere I should look to reduce memory usage?

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• Strategies for memory profiling

  In this whitepaper, Red Gate discusses the importance of handling two common issues in memory management: memory leaks and excessive memory usage. Red Gate demonstrates how their ANTS Memory Profiler can identify issues with memory management and provide a detailed view of a program's memory usage. This whitepaper doubles as a brief tutorial for using the ANTS Memory Profiler by providing an example of a program that is experiencing memory management issues.

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• Vmstat indicates memory is disappearing

  - by jimbotron

  I wanted to profile the memory usage of a script. Here's the output before it was running: procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 0 0 15624 186660 39460 439052 0 0 0 2 1 1 0 0 100 0 Here's the output while the script is running, at the point where free memory was at its lowest value: procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 0 0 15624 11464 40312 473524 0 0 0 2 1 1 0 0 100 0 So free memory dropped by about 175 MB, and I expected that buff would increase by that amount. But it seems the other columns changed by relatively negligible amounts - how is this possible? Am I interpreting this wrong, or is some memory just not being accounted for in this output?

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• Motherboard memory question

  - by JERiv

  I am currently drawing up specs on a new workstation for my office. I am considering the Asus P6X58D for a motherboard. This board's specs list it as supporting 24 gigs of memory. Suppose I were to use six four gig memory cards and then two video cards with 1 gig of memory apiece. Is the maximum supported memory similar to how 32 bit operating systems only have enough address space for 4 gigs of memory? Simply: Will the board post? If so, will the system be able to address all the memory, both the 24 gigs on the ddr3 bus and the 3 gigs on the graphics card?

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• create vmware virtual machine via command line on linux system

  - by tom smith

  evaluating/investigating vmware, and how you create a "virtual machine" using the command line for rhel/centos. basically, i want to be able to create a test virtual machine and then be able to run the VM on another system using the virtual player. so, i'm looking for pointers/articles/instructions that detail what i need (in terms of tools/apps) and the steps needed to accomplish this. i've seen a few articles/sites that discuss creating virtual machines, but they all involve using the GUI. thanks update:: while vmware is the company. there are different tools/apps provided to create a Virtual Machine. Basically, I want to do a test, to ultimately have a Virtual Machine/Image that can be run on a separate server using the vmplayer app I've seen docs that discuss using the GUI to create the VM, but haven't found any (yet) that discuss how to accomplish this using the command line approach. thanks...

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• Low CPU/Memory/Memory-bandwith Pathfinding (maybe like in Warcraft 1)

  - by Valmond

  Dijkstra and A* are all nice and popular but what kind of algorithm was used in Warcraft 1 for pathfinding? I remember that the enemy could get trapped in bowl-like caverns which means there were (most probably) no full-path calculations from "start to end". If I recall correctly, the algorithm could be something like this: A) Move towards enemy until success or hitting a wall B) If blocked by a wall, follow the wall until you can move towards the enemy without being blocked and then do A) But I'd like to know, if someone knows :-) [edit] As explained to Byte56, I'm searching for a low cpu/mem/mem-bandwidth algo and wanted to know if Warcraft had some special secrets to deliver (never seen that kind of pathfinding elsewhere), I hope that that is more concordant with the stackexchange rules.

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• Virtual PC on Windows 7 doesn't have adjustment for video card size?

  - by Jian Lin

  The current VirtualBox has a place where the video card size can be set by the user. It seems that Win 7's Virtual PC doesn't have one? Will it auto adjust -- but what if the screen size is 800 x 600 and the user resize it to 1600 x 1200, then the original video size may not be enough and will that cause any issue? I do sometimes see blinking random pixel region showing on the VPC's screen... maybe it is cause by not enough video RAM size?

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