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• SQL Authority News – Play by Play with Pinal Dave – A Birthday Gift

  - by Pinal Dave

  Today is my birthday. Personal Note When I was young, I was always looking forward to my birthday as on this day, I used to get gifts from everybody. Now when I am getting old on each of my birthday, I have almost same feeling but the direction is different. Now on each of my birthday, I feel like giving gifts to everybody. I have received lots of support, love and respect from everybody; and now I must return it back.Well, on this birthday, I have very unique gifts for everybody – my latest course on SQL Server. How I Tune Performance I often get questions where I am asked how do I work on a normal day. I am often asked that how do I work when I have performance tuning project is assigned to me. Lots of people have expressed their desire that they want me to explain and demonstrate my own method of solving performance problem when I am facing real world problem. It is a pretty difficult task as in the real world, nothing goes as planned and usually planned demonstrations have no place there. The real world, demands real solutions and in a timely fashion. If a consultant goes to industry and does not demonstrate his/her capabilities in very first few minutes, it does not matter how much fame he/she is, the door is shown to them eventually. It is true and in my early career, I have faced it quite commonly. I have learned the trick to be honest from the start and request absolutely transparent communication from the organization where I am to consult. Play by Play Play by Play is a very unique setup. It is not planned and it is a step by step course. It is like a reality show – a very real encounter to the problem and real problem solving approach. I had a great time doing this course. Geoffrey Grosenbach (VP of Pluralsight) sits down with me to see what a SQL Server Admin does in the real world. This Play-by-Play focuses on SQL Server performance tuning and I go over optimizing queries and fine-tuning the server. The table of content of this course is very simple. Introduction In the introduction I explained my basic strategies when I am approached by a customer for performance tuning. Basic Information Gathering In this module I explain how I do gather various information for performance tuning project. It is very crucial to demonstrate to customers for consultant his capability of solving problem. I attempt to resolve a small problem which gives a big positive impact on performance, consultant have to gather proper information from the start. I demonstrate in this module, how one can collect all the important performance tuning metrics. Removing Performance Bottleneck In this module, I build upon the previous module’s statistics collected. I analysis various performance tuning measures and immediately start implementing various tweaks on the performance, which will start improving the performance of my server. This is a very effective method and it gives immediate return of efforts. Index Optimization Indexes are considered as a silver bullet for performance tuning. However, it is not true always there are plenty of examples where indexes even performs worst after implemented. The key is to understand a few of the basic properties of the index and implement the right things at the right time. In this module, I describe in detail how to do index optimizations and what are right and wrong with Index. If you are a DBA or developer, and if your application is running slow – this is must attend module for you. I have some really interesting stories to tell as well. Optimize Query with Rewrite Every problem has more than one solution, in this module we will see another very famous, but hard to master skills for performance tuning – Query Rewrite. There are few do’s and don’ts for any query rewrites. I take a very simple example and demonstrate how query rewrite can improve the performance of the query at many folds. I also share some real world funny stories in this module. This course is hosted at Pluralsight. You will need a valid login for Pluralsight to watch  Play by Play: Pinal Dave course. You can also sign up for FREE Trial of Pluralsight to watch this course. As today is my birthday – I will give 10 people (randomly) who will express their desire to learn this course, a free code. Please leave your comment and I will send you free code to watch this course for free. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Training, SQLAuthority News, T SQL, Video

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• SQL SERVER – Weekly Series – Memory Lane – #053 – Final Post in Series

  - by Pinal Dave

  It has been a fantastic journey to write memory lane series for an entire year. This series gave me the opportunity to go back and see what I have contributed to this blog throughout the last 7 years. This was indeed fantastic series as this provided me the opportunity to witness how technology has grown throughout the year and how I have progressed in my career while writing this blog post. This series was indeed fantastic experience readers as many joined during the last few years and were not sure what they have missed in recent years. Let us continue with the final episode of the Memory Lane Series. 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 Get Current User – Get Logged In User Here is the straight script which list logged in SQL Server users. Disable All Triggers on a Database – Disable All Triggers on All Servers Question : How to disable all the triggers for a database? Additionally, how to disable all the triggers for all servers? For answer execute the script in the blog post. Importance of Master Database for SQL Server Startup I have received following questions many times. I will list all the questions here and answer them together. What is the purpose of Master database? Should our backup Master database? Which database is must have database for SQL Server for startup? Which are the default system database created when SQL Server 2005 is installed for the first time? What happens if Master database is corrupted? Answers to all of the questions are very much related. 2008 DECLARE Multiple Variables in One Statement SQL Server is a great product and it has many features which are very unique to SQL Server. Regarding feature of SQL Server where multiple variable can be declared in one statement, it is absolutely possible to do. 2009 How to Enable Index – How to Disable Index – Incorrect syntax near ‘ENABLE’ Many times I have seen that the index is disabled when there is a large update operation on the table. Bulk insert of very large file updates in any table using SSIS is usually preceded by disabling the index and followed by enabling the index. I have seen many developers running the following query to disable the index. 2010 List of all the Views from Database Many emails I received suggesting that they have hundreds of the view and now have no clue what is going on and how many of them have indexes and how many does not have an index. Some even asked me if there is any way they can get a list of the views with the property of Index along with it. Here is the quick script which does exactly the same. You can also include many other columns from the same view. Minimum Maximum Memory – Server Memory Options I was recently reading about SQL Server Memory Options over here. While reading this one line really caught my attention is minimum value allowed for maximum memory options. The default setting for min server memory is 0, and the default setting for max server memory is 2147483647. The minimum amount of memory you can specify for max server memory is 16 megabytes (MB). 2011 Fundamentals of Columnstore Index There are two kinds of storage in a database. Row Store and Column Store. Row store does exactly as the name suggests – stores rows of data on a page – and column store stores all the data in a column on the same page. These columns are much easier to search – instead of a query searching all the data in an entire row whether the data are relevant or not, column store queries need only to search a much lesser number of the columns. How to Ignore Columnstore Index Usage in Query In summary the question in simple words “How can we ignore using the column store index in selective queries?” Very interesting question – you can use I can understand there may be the cases when the column store index is not ideal and needs to be ignored the same. You can use the query hint IGNORE_NONCLUSTERED_COLUMNSTORE_INDEX to ignore the column store index. The SQL Server Engine will use any other index which is best after ignoring the column store index. 2012 Storing Variable Values in Temporary Array or Temporary List SQL Server does not support arrays or a dynamic length storage mechanism like list. Absolutely there are some clever workarounds and few extra-ordinary solutions but everybody can;t come up with such solution. Additionally, sometime the requirements are very simple that doing extraordinary coding is not required. Here is the simple case. Move Database Files MDF and LDF to Another Location It is not common to keep the Database on the same location where OS is installed. Usually Database files are in SAN, Separate Disk Array or on SSDs. This is done usually for performance reason and manageability perspective. Now the challenges comes up when database which was installed at not preferred default location and needs to move to a different location. Here is the quick tutorial how you can do it. UNION ALL and ORDER BY – How to Order Table Separately While Using UNION ALL If your requirement is such that you want your top and bottom query of the UNION resultset independently sorted but in the same result set you can add an additional static column and order by that column. Let us re-create the same scenario. Copy Data from One Table to Another Table – SQL in Sixty Seconds #031 – Video http://www.youtube.com/watch?v=FVWIA-ACMNo 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 – CXPACKET – Parallelism – Advanced Solution – Wait Type – Day 7 of 28

  - by pinaldave

  Earlier we discussed about the what is the common solution to solve the issue with CXPACKET wait time. Today I am going to talk about few of the other suggestions which can help to reduce the CXPACKET wait. If you are going to suggest that I should focus on MAXDOP and COST THRESHOLD – I totally agree. I have covered them in details in yesterday’s blog post. Today we are going to discuss few other way CXPACKET can be reduced. Potential Reasons: If data is heavily skewed, there are chances that query optimizer may estimate the correct amount of the data leading to assign fewer thread to query. This can easily lead to uneven workload on threads and may create CXPAKCET wait. While retrieving the data one of the thread face IO, Memory or CPU bottleneck and have to wait to get those resources to execute its tasks, may create CXPACKET wait as well. Data which is retrieved is on different speed IO Subsystem. (This is not common and hardly possible but there are chances). Higher fragmentations in some area of the table can lead less data per page. This may lead to CXPACKET wait. As I said the reasons here mentioned are not the major cause of the CXPACKET wait but any kind of scenario can create the probable wait time. Best Practices to Reduce CXPACKET wait: Refer earlier article regarding MAXDOP and Cost Threshold. De-fragmentation of Index can help as more data can be obtained per page. (Assuming close to 100 fill-factor) If data is on multiple files which are on multiple similar speed physical drive, the CXPACKET wait may reduce. Keep the statistics updated, as this will give better estimate to query optimizer when assigning threads and dividing the data among available threads. Updating statistics can significantly improve the strength of the query optimizer to render proper execution plan. This may overall affect the parallelism process in positive way. Bad Practice: In one of the recent consultancy project, when I was called in I noticed that one of the ‘experienced’ DBA noticed higher CXPACKET wait and to reduce them, he has increased the worker threads. The reality was increasing worker thread has lead to many other issues. With more number of the threads, more amount of memory was used leading memory pressure. As there were more threads CPU scheduler faced higher ‘Context Switching’ leading further degrading performance. When I explained all these to ‘experienced’ DBA he suggested that now we should reduce the number of threads. Not really! Lower number of the threads may create heavy stalling for parallel queries. I suggest NOT to touch the setting of number of the threads when dealing with CXPACKET wait. Read all the post in the Wait Types and Queue series. Note: The information presented here is from my experience and I no way claim it to be accurate. I suggest reading book on-line for further clarification. All the discussion of Wait Stats over here is generic and it varies by system to system. You are recommended to test this on development server before implementing to production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: DMV, Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• SQL SERVER – UNION ALL and ORDER BY – How to Order Table Separately While Using UNION ALL

  - by pinaldave

  I often see developers trying following syntax while using ORDER BY. SELECT Columns FROM TABLE1 ORDER BY Columns UNION ALL SELECT Columns FROM TABLE2 ORDER BY Columns However the above query will return following error. Msg 156, Level 15, State 1, Line 5 Incorrect syntax near the keyword ‘ORDER’. It is not possible to use two different ORDER BY in the UNION statement. UNION returns single resultsetand as per the Logical Query Processing Phases. However, if your requirement is such that you want your top and bottom query of the UNION resultset independently sorted but in the same resultset you can add an additional static column and order by that column. Let us re-create the same scenario. First create two tables and populated with sample data. USE tempdb GO -- Create table CREATE TABLE t1 (ID INT, Col1 VARCHAR(100)); CREATE TABLE t2 (ID INT, Col1 VARCHAR(100)); GO -- Sample Data Build INSERT INTO t1 (ID, Col1) SELECT 1, 'Col1-t1' UNION ALL SELECT 2, 'Col2-t1' UNION ALL SELECT 3, 'Col3-t1'; INSERT INTO t2 (ID, Col1) SELECT 3, 'Col1-t2' UNION ALL SELECT 2, 'Col2-t2' UNION ALL SELECT 1, 'Col3-t2'; GO If we SELECT the data from both the table using UNION ALL . -- SELECT without ORDER BY SELECT ID, Col1 FROM t1 UNION ALL SELECT ID, Col1 FROM t2 GO We will get the data in following order. However, our requirement is to get data in following order. If we need data ordered by Column1 we can ORDER the resultset ordered by Column1. -- SELECT with ORDER BY SELECT ID, Col1 FROM t1 UNION ALL SELECT ID, Col1 FROM t2 ORDER BY ID GO Now to get the data in independently sorted in UNION ALL let us add additional column OrderKey and use ORDER BY  on that column. I think the description does not do proper justice let us see the example here. -- SELECT with ORDER BY - with ORDER KEY SELECT ID, Col1, 'id1' OrderKey FROM t1 UNION ALL SELECT ID, Col1, 'id2' OrderKey FROM t2 ORDER BY OrderKey, ID GO The above query will give the desired result. Now do not forget to clean up the database by running the following script. -- Clean up DROP TABLE t1; DROP TABLE t2; GO Here is the complete script used in this example. USE tempdb GO -- Create table CREATE TABLE t1 (ID INT, Col1 VARCHAR(100)); CREATE TABLE t2 (ID INT, Col1 VARCHAR(100)); GO -- Sample Data Build INSERT INTO t1 (ID, Col1) SELECT 1, 'Col1-t1' UNION ALL SELECT 2, 'Col2-t1' UNION ALL SELECT 3, 'Col3-t1'; INSERT INTO t2 (ID, Col1) SELECT 3, 'Col1-t2' UNION ALL SELECT 2, 'Col2-t2' UNION ALL SELECT 1, 'Col3-t2'; GO -- SELECT without ORDER BY SELECT ID, Col1 FROM t1 UNION ALL SELECT ID, Col1 FROM t2 GO -- SELECT with ORDER BY SELECT ID, Col1 FROM t1 UNION ALL SELECT ID, Col1 FROM t2 ORDER BY ID GO -- SELECT with ORDER BY - with ORDER KEY SELECT ID, Col1, 'id1' OrderKey FROM t1 UNION ALL SELECT ID, Col1, 'id2' OrderKey FROM t2 ORDER BY OrderKey, ID GO -- Clean up DROP TABLE t1; DROP TABLE t2; GO I am sure there are many more ways to achieve this, what method would you use if you have to face the similar situation? Reference: Pinal Dave (http://blog.sqlauthority.com)   Filed under: Best Practices, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Big Data – Data Mining with Hive – What is Hive? – What is HiveQL (HQL)? – Day 15 of 21

  - by Pinal Dave

  In yesterday’s blog post we learned the importance of the operational database in Big Data Story. In this article we will understand what is Hive and HQL in Big Data Story. Yahoo started working on PIG (we will understand that in the next blog post) for their application deployment on Hadoop. The goal of Yahoo to manage their unstructured data. Similarly Facebook started deploying their warehouse solutions on Hadoop which has resulted in HIVE. The reason for going with HIVE is because the traditional warehousing solutions are getting very expensive. What is HIVE? Hive is a datawarehouseing infrastructure for Hadoop. The primary responsibility is to provide data summarization, query and analysis. It  supports analysis of large datasets stored in Hadoop’s HDFS as well as on the Amazon S3 filesystem. The best part of HIVE is that it supports SQL-Like access to structured data which is known as HiveQL (or HQL) as well as big data analysis with the help of MapReduce. Hive is not built to get a quick response to queries but it it is built for data mining applications. Data mining applications can take from several minutes to several hours to analysis the data and HIVE is primarily used there. HIVE Organization The data are organized in three different formats in HIVE. Tables: They are very similar to RDBMS tables and contains rows and tables. Hive is just layered over the Hadoop File System (HDFS), hence tables are directly mapped to directories of the filesystems. It also supports tables stored in other native file systems. Partitions: Hive tables can have more than one partition. They are mapped to subdirectories and file systems as well. Buckets: In Hive data may be divided into buckets. Buckets are stored as files in partition in the underlying file system. Hive also has metastore which stores all the metadata. It is a relational database containing various information related to Hive Schema (column types, owners, key-value data, statistics etc.). We can use MySQL database over here. What is HiveSQL (HQL)? Hive query language provides the basic SQL like operations. Here are few of the tasks which HQL can do easily. Create and manage tables and partitions Support various Relational, Arithmetic and Logical Operators Evaluate functions Download the contents of a table to a local directory or result of queries to HDFS directory Here is the example of the HQL Query: SELECT upper(name), salesprice FROM sales; SELECT category, count(1) FROM products GROUP BY category; When you look at the above query, you can see they are very similar to SQL like queries. Tomorrow In tomorrow’s blog post we will discuss about very important components of the Big Data Ecosystem – Pig. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• Whether to use UNION or OR in SQL Server Queries

  - by Dinesh Asanka

  Recently I came across with an article on DB2 about using Union instead of OR. So I thought of carrying out a research on SQL Server on what scenarios UNION is optimal in and which scenarios OR would be best. I will analyze this with a few scenarios using samples taken  from the AdventureWorks database Sales.SalesOrderDetail table. Scenario 1: Selecting all columns So we are going to select all columns and you have a non-clustered index on the ProductID column. --Query 1 : OR SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 714 OR ProductID =709 OR ProductID =998 OR ProductID =875 OR ProductID =976 OR ProductID =874 --Query 2 : UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 714 UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 709 UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 998 UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 875 UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 976 UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 874 So query 1 is using OR and the later is using UNION. Let us analyze the execution plans for these queries. Query 1 Query 2 As expected Query 1 will use Clustered Index Scan but Query 2, uses all sorts of things. In this case, since it is using multiple CPUs you might have CX_PACKET waits as well. Let’s look at the profiler results for these two queries: CPU Reads Duration Row Counts OR 78 1252 389 3854 UNION 250 7495 660 3854 You can see from the above table the UNION query is not performing well as the  OR query though both are retuning same no of rows (3854).These results indicate that, for the above scenario UNION should be used. Scenario 2: Non-Clustered and Clustered Index Columns only --Query 1 : OR SELECT ProductID,SalesOrderID, SalesOrderDetailID FROM Sales.SalesOrderDetail WHERE ProductID = 714 OR ProductID =709 OR ProductID =998 OR ProductID =875 OR ProductID =976 OR ProductID =874 GO --Query 2 : UNION SELECT ProductID,SalesOrderID, SalesOrderDetailID FROM Sales.SalesOrderDetail WHERE ProductID = 714 UNION SELECT ProductID,SalesOrderID, SalesOrderDetailID FROM Sales.SalesOrderDetail WHERE ProductID = 709 UNION SELECT ProductID,SalesOrderID, SalesOrderDetailID FROM Sales.SalesOrderDetail WHERE ProductID = 998 UNION SELECT ProductID,SalesOrderID, SalesOrderDetailID FROM Sales.SalesOrderDetail WHERE ProductID = 875 UNION SELECT ProductID,SalesOrderID, SalesOrderDetailID FROM Sales.SalesOrderDetail WHERE ProductID = 976 UNION SELECT ProductID,SalesOrderID, SalesOrderDetailID FROM Sales.SalesOrderDetail WHERE ProductID = 874 GO So this time, we will be selecting only index columns, which means these queries will avoid a data page lookup. As in the previous case we will analyze the execution plans: Query 1 Query 2 Again, Query 2 is more complex than Query 1. Let us look at the profile analysis: CPU Reads Duration Row Counts OR 0 24 208 3854 UNION 0 38 193 3854 In this analyzis, there is only slight difference between OR and UNION. Scenario 3: Selecting all columns for different fields Up to now, we were using only one column (ProductID) in the where clause.  What if we have two columns for where clauses and let us assume both are covered by non-clustered indexes? --Query 1 : OR SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 714 OR CarrierTrackingNumber LIKE 'D0B8%' --Query 2 : UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 714 UNION SELECT * FROM Sales.SalesOrderDetail WHERE CarrierTrackingNumber  LIKE 'D0B8%' Query 1 Query 2: As we can see, the query plan for the second query has improved. Let us see the profiler results. CPU Reads Duration Row Counts OR 47 1278 443 1228 UNION 31 1334 400 1228 So in this case too, there is little difference between OR and UNION. Scenario 4: Selecting Clustered index columns for different fields Now let us go only with clustered indexes: --Query 1 : OR SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 714 OR CarrierTrackingNumber LIKE 'D0B8%' --Query 2 : UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 714 UNION SELECT * FROM Sales.SalesOrderDetail WHERE CarrierTrackingNumber  LIKE 'D0B8%' Query 1 Query 2 Now both execution plans are almost identical except is an additional Stream Aggregate is used in the first query. This means UNION has advantage over OR in this scenario. Let us see profiler results for these queries again. CPU Reads Duration Row Counts OR 0 319 366 1228 UNION 0 50 193 1228 Now see the differences, in this scenario UNION has somewhat of an advantage over OR. Conclusion Using UNION or OR depends on the scenario you are faced with. So you need to do your analyzing before selecting the appropriate method. Also, above the four scenarios are not all an exhaustive list of scenarios, I selected those for the broad description purposes only.

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• SQL SERVER – Puzzle to Win Print Book – Functions FIRST_VALUE and LAST_VALUE with OVER clause and ORDER BY

  - by pinaldave

  Some time an interesting feature and smart audience makes total difference at places. From last two days, I have been writing on SQL Server 2012 feature FIRST_VALUE and LAST_VALUE. Please read following post before I continue today as this question is based on the same. Introduction to FIRST_VALUE and LAST_VALUE Introduction to FIRST_VALUE and LAST_VALUE with OVER clause As a comment of the second post I received excellent question from Nilesh Molankar. He asks what will happen if we change few things in the T-SQL. I really like this question as this kind of questions will make us sharp and help us perform in critical situation in need. We recently publish SQL Server Interview Questions book. I promise that in future version of this book, we will for sure include this question. Instead of repeating his question, I am going to ask something very similar to his question. Let us first run following query (read yesterday’s blog post for more detail): USE AdventureWorks GO SELECT s.SalesOrderID,s.SalesOrderDetailID,s.OrderQty, FIRST_VALUE(SalesOrderDetailID) OVER (PARTITION BY SalesOrderID ORDER BY SalesOrderDetailID ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) FstValue, LAST_VALUE(SalesOrderDetailID) OVER (PARTITION BY SalesOrderID ORDER BY SalesOrderDetailID ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) LstValue FROM Sales.SalesOrderDetail s WHERE SalesOrderID IN (43670, 43669, 43667, 43663) ORDER BY s.SalesOrderID,s.SalesOrderDetailID,s.OrderQty GO Here is the resultset of the above query. Now let us change the ORDER BY clause of OVER clause in above query and see what is the new result. USE AdventureWorks GO SELECT s.SalesOrderID,s.SalesOrderDetailID,s.OrderQty, FIRST_VALUE(SalesOrderDetailID) OVER (PARTITION BY SalesOrderID ORDER BY OrderQty ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) FstValue, LAST_VALUE(SalesOrderDetailID) OVER (PARTITION BY SalesOrderID ORDER BY OrderQty ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) LstValue FROM Sales.SalesOrderDetail s WHERE SalesOrderID IN (43670, 43669, 43667, 43663) ORDER BY s.SalesOrderID,s.SalesOrderDetailID,s.OrderQty GO Now let us see the result and ready for interesting question: Puzzle 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. Hint Let me give you a simple hint. Just for simplicity I have changed the order of columns selected in the SELECT and ORDER BY (at the end). This will not change resultset but just order of the columns as well order of the rows. However, the data remains the same. USE AdventureWorks GO SELECT s.OrderQty,s.SalesOrderID,s.SalesOrderDetailID, FIRST_VALUE(SalesOrderDetailID) OVER (PARTITION BY SalesOrderID ORDER BY OrderQty ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) FstValue, LAST_VALUE(SalesOrderDetailID) OVER (PARTITION BY SalesOrderID ORDER BY OrderQty ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) LstValue FROM Sales.SalesOrderDetail s WHERE SalesOrderID IN (43670, 43669, 43667, 43663) ORDER BY s.OrderQty,s.SalesOrderID,s.SalesOrderDetailID GO Above query returns following result: Now I am very sure all of you have figured out the solution. Here is the second hint – pay attention to row 2, 3, 4, and 10. Hint2 T-SQL Enhancements: FIRST_VALUE() and LAST_VALUE() MSDN: FIRST_VALUE and LAST_VALUE Rules Leave a comment with your detailed answer by Nov 15′s blog post. Open world-wide (where Amazon ships books) If you blog about puzzle’s solution and if you win, you win additional surprise gift as well. Prizes Print copy of my new book SQL Server Interview Questions Amazon|Flipkart If you already have this book, you can opt for any of my other books SQL Wait Stats [Amazon|Flipkart|Kindle] and SQL Programming [Amazon|Flipkart|Kindle]. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Visual Studio Find and Replace Regular Expressions ~ find lines with quoted strings, not containing

  - by Darkoni

  Visual Studio Find and Replace Regular Expressions Find lines with quoted strings, not containing strings include or trace i am tryling to find out all lines in c++ project that contains some text as i have to use visual studio, i have to use its Find and Replace http://www.codinghorror.com/blog/2006/07/the-visual-studio-ide-and-regular-expressions.html so, for finding all lines like: print("abc"); it is enogh to write :q and it will find all quotted strings ok, but i also get lot of lines like #include "stdio.h" and trace("* step 1 *") i find out regex to get all lines containing include and trace <include|trace> so, mine question is, how to find all lines with "quotted strings" but NOT lines that contains strings include and trace. thanx

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• How do you unit test a LINQ query using Moq and Machine.Specifications?

  - by Phil.Wheeler

  I'm struggling to get my head around how to accommodate a mocked repository's method that only accepts a Linq expression as its argument. Specifically, the repository has a First() method that looks like this: public T First(Expression<Func<T, bool>> expression) { return All().Where(expression).FirstOrDefault(); } The difficulty I'm encountering is with my MSpec tests, where I'm (probably incorrectly) trying to mock that call: public abstract class with_userprofile_repository { protected static Mock<IRepository<UserProfile>> repository; Establish context = () => { repository = new Mock<IRepository<UserProfile>>(); repository.Setup<UserProfile>(x => x.First(up => up.OpenID == @"http://testuser.myopenid.com")).Returns(GetDummyUser()); }; protected static UserProfile GetDummyUser() { UserProfile p = new UserProfile(); p.OpenID = @"http://testuser.myopenid.com"; p.FirstName = "Joe"; p.LastLogin = DateTime.Now.Date.AddDays(-7); p.LastName = "Bloggs"; p.Email = "[email protected]"; return p; } } I run into trouble because it's not enjoying the Linq expression: System.NotSupportedException: Expression up = (up.OpenID = "http://testuser.myopenid.com") is not supported. So how does one test these sorts of scenarios?

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• Regular expression for Regular expressions?

  - by kavoir.com

  I have an app that enables the user to input a regular expression, my question is how to check against any input of regular expressions and make sure they are valid ones because if they are not there will be preg_match errors. I don't want to use the '@' before preg_match, so if there's a way to check the validity of the user input of regular expressions that'd be great. The regular expression system of PHP seems to be rather too complicated for me to come up with a regular expression for them. Any idea or any alternatives would be possible in achieving this?

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• Sharepoint dynamic caml query problem?

  - by AB

  Hi, I want to dynamic caml query based on query string.Let me explain it with example my query sting can be anything ?cat=ABC&cat=ABD&cat=ABE... ?Cat=ABC ?Cat=ABC&cat=ABL so no. can be anything now the problem begins I want to query my sharepoint list based on this query string if (HttpContext.Current.Request.QueryString["cat"] != null) { string _cat = HttpContext.Current.Request.QueryString["cat"].ToString(); } so this way my string contains all the query string _cat=ABC,AD,....all. I want to query my sharepoint list based on these query string and with "AND" where title=ABC and title=AD .... if there is only one query string then only where title=ABC....so I want my query string should be dynamic.... Any idea how to acheive this??

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• Double interpolation of regular expressions in Perl

  - by tomdee

  I have a Perl program that stores regular expressions in configuration files. They are in the form: regex = ^/d+$ Elsewhere, the regex gets parsed from the file and stored in a variable - $regex. I then use the variable when checking the regex, e.g. $lValid = ($valuetocheck =~ /$regex/); I want to be able to include perl variables in the config file, e.g. regex = ^\d+$stored_regex$ But I can't work out how to do it. When regular expressions are parsed by Perl they get interpreted twice. First the variables are expanded, and then the the regular expression itself is parsed. What I need is a three stage process: First interpolate $regex, then interpolate the variables it contains and then parse the resulting regular expression. Both the first two interpolations need to be "regular expression aware". e.g. they should know that the string contain $ as an anchor etc... Any ideas?

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• Lua pattern matching vs. regular expressions

  - by harald

  hello, i'm currently learning lua. regarding pattern-matching in lua i found the following sentence in the lua documentation on lua.org: Nevertheless, pattern matching in Lua is a powerful tool and includes some features that are difficult to match with standard POSIX implementations. as i'm familiar with posix regular expressions i would like to know if there are any common samples where lua pattern matching is "better" compared to regular expression -- or did i misinterpret the sentence? and if there are any common examples: why is any of pattern-matching vs. regular expressions better suited? thanks very much, harald

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• lambda expressions in C#?

  - by Matt

  Hey I'm rather new to these could someone explain the significance (of the following code) or prehaps give a link to some useful information on lambda expressions? I encounter the following code in a test and I am wondering why someone would do this: foo.MyEvent += (o, e) => { fCount++; Console.WriteLine(fCount); }; foo.MyEvent -= (o, e) => { fCount++; Console.WriteLine(fCount); }; My instinct tells me it is something simple and not a mistake, but I don't know enough about these expressions to understand why this is being done. Regards,

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• Regular expressions in findstr

  - by Johannes Rössel

  I'm doing a little string validation with findstr and its /r flag to allow for regular expressions. In particular I'd like to validate integers. The regex ^[0-9][0-9]*$ worked fine for non-negative numbers but since I now support negative numbers as well I tried ^([1-9][0-9]*|0|-[1-9][0-9]*)$ for either positive or negative integers or zero. The regex works fine theoretically. I tested it in PowerShell and it matches what I want. However, with findstr /r /c:"^([1-9][0-9]*|0|-[1-9][0-9]*)$" it doesn't. While I know that findstr doesn't have the most advanced regex support (even below Notepad++ which is probably quite an achievement), I would have expected such simple expressions to work. Any ideas what I'm doing wrong here?

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• Code Golf: Evaluating Mathematical Expressions

  - by Noldorin

  Challenge Here is the challenge (of my own invention, though I wouldn't be surprised if it has previously appeared elsewhere on the web). Write a function that takes a single argument that is a string representation of a simple mathematical expression and evaluates it as a floating point value. A "simple expression" may include any of the following: positive or negative decimal numbers, +, -, *, /, (, ). Expressions use (normal) infix notation. Operators should be evaluated in the order they appear, i.e. not as in BODMAS, though brackets should be correctly observed, of course. The function should return the correct result for any possible expression of this form. However, the function does not have to handle malformed expressions (i.e. ones with bad syntax). Examples of expressions: 1 + 3 / -8 = -0.5 (No BODMAS) 2*3*4*5+99 = 219 4 * (9 - 4) / (2 * 6 - 2) + 8 = 10 1 + ((123 * 3 - 69) / 100) = 4 2.45/8.5*9.27+(5*0.0023) = 2.68... Rules I anticipate some form of "cheating"/craftiness here, so please let me forewarn against it! By cheating, I refer to the use of the eval or equivalent function in dynamic languages such as JavaScript or PHP, or equally compiling and executing code on the fly. (I think my specification of "no BODMAS" has pretty much guaranteed this however.) Apart from that, there are no restrictions. I anticipate a few Regex solutions here, but it would be nice to see more than just that. Now, I'm mainly interested in a C#/.NET solution here, but any other language would be perfectly acceptable too (in particular, F# and Python for the functional/mixed approaches). I haven't yet decided whether I'm going to accept the shortest or most ingenious solution (at least for the language) as the answer, but I would welcome any form of solution in any language, except what I've just prohibited above! My Solution I've now posted my C# solution here (403 chars). Update: My new solution has beaten the old one significantly at 294 chars, with the help of a bit of lovely regex! I suspected that this will get easily beaten by some of the languages out there with lighter syntax (particularly the funcional/dynamic ones), and have been proved right, but I'd be curious if someone could beat this in C# still. Update I've seen some very crafty solutions already. Thanks to everyone who has posted one. Although I haven't tested any of them yet, I'm going to trust people and assume they at least work with all of the given examples. Just for the note, re-entrancy (i.e. thread-safety) is not a requirement for the function, though it is a bonus. Format Please post all answers in the following format for the purpose of easy comparison: Language Number of characters: ??? Fully obfuscated function: (code here) Clear/semi-obfuscated function: (code here) Any notes on the algorithm/clever shortcuts it takes.

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• Using numeric_limits::max() in constant expressions

  - by FireAphis

  Hello, I would like to define inside a class a constant which value is the maximum possible int. Something like this: class A { ... static const int ERROR_VALUE = std::numeric_limits<int>::max(); ... } This declaration fails to compile with the following message: numeric.cpp:8: error: 'std::numeric_limits::max()' cannot appear in a constant-expression numeric.cpp:8: error: a function call cannot appear in a constant-expression I understand why this doesn't work, but two things look weird to me: It seems to me a natural decision to use the value in constant expressions. Why did the language designers decide to make max() a function thus not allowing this usage? The spec claims in 18.2.1 that For all members declared static const in the numeric_limits template, specializations shall define these values in such a way that they are usable as integral constant expressions. Doesn't it mean that I should be able to use it in my scenario and doesn't it contradict the error message? Thank you.

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• In C#, are Lamba Expressions objects?

  - by Brian Warshaw

  In C#, are lambda expressions objects? If so, what sort of object are they?

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• .NET Regular expressions on bytes instead of chars

  - by brickner

  Hi, I'm trying to do some parsing that will be easier using regular expressions. The input is an array (or enumeration) of bytes. I don't want to convert the bytes to chars for the following reasons: Computation efficiency Memory consumption efficiency Some non-printable bytes might be complex to convert to chars. Not all the bytes are printable. So I can't use Regex. The only solution I know, is using Boost.Regex (which works on bytes - C chars), but this is a C++ library that wrapping using C++/CLI will take considerable work. How can I use regular expressions on bytes in .NET directly, without working with .NET strings and chars? Thank you.

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• Add values to standard expressions list in Regular Expression Editor dialog in VS 2008

  - by Alex

  Hi. In the "Regular Expression Editor" dialog in VS 2008 ( or 2005 for this matter ) , there is a list of "standard expressions" like : "French phone number" , "French postal code" etc.. And of course there is an option to select a "Custom" and then enter your own regular expression. Well.. I want to add a predefined expressions to that list . Like : "Israeli phone number" . I don't want to enter it every time by selecting a custom value . I want my developers in the team available items for them to choose. Anyone knows how to alter that list ? I've found some question about it on the web - and the answer given is that it's not possible . But that was at 2004. Anyone ?!?! Thanks.

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• Insert string from database into an aspx and have databinding expressions within that text evaluated

  - by Christopher Edwards

  Well, as you can see I want something quick-and-dirty! How can I get a string from a db that has aspx databinding syntax in it and have the databinding expressions evaluated? So I have text such as this stored in the DB:- Hello <%=User.Name %> I haven't seen you since <%=User.LastVisit %> And I want it to be inserted here say:- ... <body> <form id="form1" runat="server"> <div> <asp:FormView ID="FormView1" DataSourceID="DataSource1" runat="server"> <ItemTemplate> <-- insert stuff here! --> ... But with the databinding expressions evaluated. I'd rather not build a full parsing, templating and evaluation engine...

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• template expressions and visual studio 2005 c++

  - by chris

  I'd like to build the olb3d library with my visual studio 2005 compiler but this failes due to template errors. To be more specific, the following expression seem to be a problem: void function(T u[Lattice::d]) On the website of the project is stated that prpably my compiler is not capable of such complicated template expressions - one should use the gcc 3.4.1. My question is now if there is a way to upgrade my vs c++ compiler so it can handle template expressions on the level as the gcc 3.4.1? Maybe it helps if I get a newer version of visual studio? Cheers C.

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• php array regular expressions

  - by bell

  I am using regular expressions in php to match postcodes found in a string. The results are being returned as an array, I was wondering if there is any way to assign variables to each of the results, something like $postcode1 = first match found $postcode2 = second match found here is my code $html = "some text here bt123ab and another postcode bt112cd"; preg_match_all("/([a-zA-Z]{2})([0-9]{2,3})([a-zA-Z]{2})/", $html, $matches, PREG_SET_ORDER); foreach ($matches as $val) { echo $val[0]; } I am very new to regular expressions and php, forgive me if this is a stupid question. Thanks in advance

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• could not resolve property (complex properties)

  - by felipeoriani

  I have a asp.net mvc application with NHibernate and I do not know how to resolve a problem to query some data. I have this query: // create query var query = session.QueryOVer<Laudo>().Fetch(x => x.Equipament).Eager; // add some filters if (idEquipament.HasValue) query = query.And(x => x.Equipament.Id == idEquipament.Value); //I got the error here... if (idCompany.HasValue) query = query.And(x => x.Equipament.Company.Id == idCompany.Value); When I try to execute this query, I've got an exception with this message: "could not resolve property: Equipament.Company.Id of: DomainModel.Laudo" what can I do to fix this problem? Thanks

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• SQL SEVER – Finding Memory Pressure – External and Internal

  - by pinaldave

  Following query will provide details of external and internal memory pressure. It will return the data how much portion in the existing memory is assigned to what kind of memory type. SELECT TYPE, SUM(single_pages_kb) InternalPressure, SUM(multi_pages_kb) ExtermalPressure FROM sys.dm_os_memory_clerks GROUP BY TYPE ORDER BY SUM(single_pages_kb) DESC, SUM(multi_pages_kb) DESC GO What is your method to find memory pressure? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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