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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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• Transitioning from Oracle based CMS to MySQL based CMS

  - by KM01

  We're looking at a replacement for our CMS which runs on Oracle. The new CMSes that we've looked at can in theory run on Oracle, but most of the vendor's installs run off of MySQL vendor supports install of their CMS on MySQL, and a "theoretical" install on Oracle the vendor's dev shops use MySQL none of them develop/test against Oracle Our DBA team works exclusively with Oracle, and doesn't have the bandwidth to provide additional support for a highly available and performing MySQL setup. They could in theory go to training and get ramped up, but our time line is also short (surprise!). So ... I guess my question(s) are: If you've seen a situation like this, how have you dealt with it? What tipped the balance either way? What type of effort did it take? If you're to do it over, what would you do differently ... ? Thanks! KM

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• SQL SERVER – Introduction to PERCENTILE_DISC() – Analytic Functions Introduced in SQL Server 2012

  - by pinaldave

  SQL Server 2012 introduces new analytical function PERCENTILE_DISC(). The book online gives following definition of this function: Computes a specific percentile for sorted values in an entire rowset or within distinct partitions of a rowset in Microsoft SQL Server 2012 Release Candidate 0 (RC 0). For a given percentile value P, PERCENTILE_DISC sorts the values of the expression in the ORDER BY clause and returns the value with the smallest CUME_DIST value (with respect to the same sort specification) that is greater than or equal to P. If you are clear with understanding of the function – no need to read further. If you got lost here is the same in simple words – find value of the column which is equal or more than CUME_DIST. Before you continue reading this blog I strongly suggest you read about CUME_DIST function over here Introduction to CUME_DIST – Analytic Functions Introduced in SQL Server 2012. Now let’s have fun following query: USE AdventureWorks GO SELECT SalesOrderID, OrderQty, ProductID, CUME_DIST() OVER(PARTITION BY SalesOrderID ORDER BY ProductID ) AS CDist, PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY ProductID) OVER (PARTITION BY SalesOrderID) AS PercentileDisc FROM Sales.SalesOrderDetail WHERE SalesOrderID IN (43670, 43669, 43667, 43663) ORDER BY SalesOrderID DESC GO The above query will give us the following result: You can see that I have used PERCENTILE_DISC(0.5) in query, which is similar to finding median but not exactly. PERCENTILE_DISC() function takes a percentile as a passing parameters. It returns the value as answer which value is equal or great to the percentile value which is passed into the example. For example in above example we are passing 0.5 into the PERCENTILE_DISC() function. It will go through the resultset and identify which rows has values which are equal to or great than 0.5. In first example it found two rows which are equal to 0.5 and the value of ProductID of that row is the answer of PERCENTILE_DISC(). In some third windowed resultset there is only single row with the CUME_DIST() value as 1 and that is for sure higher than 0.5 making it as a answer. To make sure that we are clear with this example properly. Here is one more example where I am passing 0.6 as a percentile. Now let’s have fun following query: USE AdventureWorks GO SELECT SalesOrderID, OrderQty, ProductID, CUME_DIST() OVER(PARTITION BY SalesOrderID ORDER BY ProductID ) AS CDist, PERCENTILE_DISC(0.6) WITHIN GROUP (ORDER BY ProductID) OVER (PARTITION BY SalesOrderID) AS PercentileDisc FROM Sales.SalesOrderDetail WHERE SalesOrderID IN (43670, 43669, 43667, 43663) ORDER BY SalesOrderID DESC GO The above query will give us the following result: The result of the PERCENTILE_DISC(0.6) is ProductID of which CUME_DIST() is more than 0.6. This means for SalesOrderID 43670 has row with CUME_DIST() 0.75 is the qualified row, resulting answer 773 for ProductID. I hope this explanation makes it further clear. 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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• best practice? Consumer data in MySQL on Amazon EBS (Elastic block store)

  - by jeff7091

  This is a consumer app, so I will care about storage costs - I don't want to have 5x copies of data lying about. The app shards very well, so I can use MySQL and not have scaling issues. Amazon EBS has a nice baseline+snapshot backup capability that uses S3. This should have a light footprint (in terms of storage cost). BUT: the magnolia.com story scares the crap out of me: basically flawless block-level backup of a corrupt DB or filesystem. Is there anything that is nearly as storage efficient as EBS at the MySQL level?

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• On MySQL 5.1 for Windows, why can't I assign DBA role to the "root" user?

  - by djangofan

  On MySQL 5.1 for Windows, why can't I assign DBA role to "root" user? The MySQL Workbench allows me to add all the other roles except for DBA. Also, when I "alter schema" on any table, while logged in as root, I dont see all the tabs that show me all the database properties... I only see the first tab that allows me to change collation only. What is wrong with this picture? How do i give root all priveleges? I've tried a few variations of GRANT ALL PRIVILEGES etc. from the command line but nothing works. My root account is unable to alter column names, indexes, or options of any given table that I create. I can create tables and delete them but I can't alter them.

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• "MySQL Highlights" at DrupalCon

  - by christopher.jones

  Following on from my earlier post, also at DrupalCon is John Duncan, presenting MySQL Highlights on Tuesday, a session that looks very interesting. John is a long-time MySQL person, having worked at MySQL AB prior to Sun and Oracle acquisitions.

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• Ubuntu: How can i delete my password of mysql(I dont want password)?

  - by meyosef

  Ubuntu: How can i delete my password of mysql(I dont want password to enter to my database)? Thanks, Yosef

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• To Do list for multiple users using MySQL, Need some advice regarding Projectwork?

  - by Steve

  i am thinking to create a To Do list sort of thing for my Project work. it's sort of a To do list type thing, meant for Multiple Users. i mean each user will have his Login and Password , to access into his account or profile and from there he/she can Manage his own To-Do list. it's has to be Kind of like Remember the Milk sort of. Every user will have his own To Do list. i mean now as Different users will have Different To Dos to perform and so different To Dos Lists, if for data fields like in tabular form. Task || Priority || Deadline || Number of days required ||Status. -----||----------||----------||-------------------------||-------------------- -----||----------||----------||-------------------------||-------------------- -----||----------||----------||-------------------------||-------------------- So what i meant to ask , Can this type of thing be done using MySQL as database and and any web based server side language PHP, ASP, JSP. i mean Can this be done through RDBMS like MySQL, for here different member users will have different to do lists than each others to keep and maintain.

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• Apache and MySQL taking all the memory? Maximum connections?

  - by lpfavreau

  I've a had one of our servers going down (network wise) but keeping its uptime (so looks the server is not losing its power) recently. I've asked my hosting company to investigate and I've been told, after investigation, that Apache and MySQL were at all time using 80% of the memory and peaking at 95% and that I might be needing to add some more RAM to the server. One of their justifications to adding more RAM was that I was using the default max connections setting (125 for MySQL and 150 for Apache) and that for handling those 150 simultaneous connections, I would need at least 3Gb of memory instead of the 1Gb I have at the moment. Now, I understand that tweaking the max connections might be better than me leaving the default setting although I didn't feel it was a concern at the moment, having had servers with the same configuration handle more traffic than the current 1 or 2 visitors before the lunch, telling myself I'd tweak it depending on the visits pattern later. I've also always known Apache was more memory hungry under default settings than its competitor such as nginx and lighttpd. Nonetheless, looking at the stats of my machine, I'm trying to see how my hosting company got those numbers. I'm getting: # free -m total used free shared buffers cached Mem: 1000 944 56 0 148 725 -/+ buffers/cache: 71 929 Swap: 1953 0 1953 Which I guess means that yes, the server is reserving around 95% of its memory at the moment but I also thought it meant that only 71 out of the 1000 total were really used by the applications at the moment looking a the buffers/cache row. Also I don't see any swapping: # vmstat 60 procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 0 0 0 57612 151704 742596 0 0 1 1 3 11 0 0 100 0 0 0 0 57604 151704 742596 0 0 0 1 1 24 0 0 100 0 0 0 0 57604 151704 742596 0 0 0 2 1 18 0 0 100 0 0 0 0 57604 151704 742596 0 0 0 0 1 13 0 0 100 0 And finally, while requesting a page: top - 08:33:19 up 3 days, 13:11, 2 users, load average: 0.06, 0.02, 0.00 Tasks: 81 total, 1 running, 80 sleeping, 0 stopped, 0 zombie Cpu(s): 1.3%us, 0.3%sy, 0.0%ni, 98.3%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 1024616k total, 976744k used, 47872k free, 151716k buffers Swap: 2000052k total, 0k used, 2000052k free, 742596k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 24914 www-data 20 0 26296 8640 3724 S 2 0.8 0:00.06 apache2 23785 mysql 20 0 125m 18m 5268 S 1 1.9 0:04.54 mysqld 24491 www-data 20 0 25828 7488 3180 S 1 0.7 0:00.02 apache2 1 root 20 0 2844 1688 544 S 0 0.2 0:01.30 init ... So, I'd like to know, experts of serverfault: Do I really need more RAM at the moment? How do they calculate that for 150 simultaneous connections I'd need 3Gb? Thanks for your help!

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• DRBD and MySQL - Heartbeat Setup

  Heartbeat automates all the moving parts and can work as well with the MySQL master-master active/passive solution as well as it can with the MySQL & DRBD solution. It manages the virtual IP address used by the database, directs DRBD to become primary, or relinquish primary duties, mounts the /dev/drbd0 device, and starts/stops MySQL as needed.

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• DRBD and MySQL - Heartbeat Setup

  Heartbeat automates all the moving parts and can work as well with the MySQL master-master active/passive solution as well as it can with the MySQL & DRBD solution. It manages the virtual IP address used by the database, directs DRBD to become primary, or relinquish primary duties, mounts the /dev/drbd0 device, and starts/stops MySQL as needed.

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• How to use Binary Log file for Auditing and Replicating in MySQL?

  - by Pranav

  How to use Binary Log file for Auditing in MySQL? I want to track the change in a DB using Binary Log so that I can replicate these changes to other DB please do not give me hyperlinks for MySQL website. please direct me to find the solution EDIT I have looked for auditing options and created a script using Triggers for that, but due toi the Joomla DB structure it did'nt worked for me, hence I have to move on to Binary Log file concept now i am stucked in initiating the concept as I am not getting the concept of making the server master/slave, so can any body guide me how to actually initiate it via PHP?

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• How to establish the real-time communication between Shopping cart running MySQL and Internal System Running PostgreSQL [closed]

  - by Andrew

  I am thinking about the way of establishing some-sort of real-time connection between MySQLpowered shopping cart and internal system that is running on PostgreSQL. Could you give me some sort of insight on this topic? For example, I can write some sort of csv export application, then enable remote MySQL for over the internet connection and then import csv to mysql directly from PC. Or upload csv and run cron on server. But this way of import-export causing delays; so I would like to link databased (or some msort). I have never done it before and would like to hear some opinions about this. Another way "just a thought" might to implement triggers that would initiate the update process via csv; but again, I would like to avoid csv. Do you have any good advise? Maybe some specific examples?

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• MySQL Enterprise Backup 3.8.2 - Overview

  - by Priya Jayakumar

    MySQL Enterprise Backup (MEB) is the ideal solution for backing up MySQL databases. MEB 3.8.2 is released in June 2013. MySQL Enterprise Backup 3.8.2 release’s main goal is to improve usability. With this release, users can know the progress of backup completed both in terms of size and as a percentage of the total. This release also offers options to be able to manage the behavior of MEB in case the space on the secondary storage is completely exhausted during backup. The progress indicator is a (short) string that indicates how far the execution of a time-consuming MEB command has progressed. It consists of one or more "meters" that measures the progress of the command. There are two options introduced to control the progress reporting function of mysqlbackup command (1) –show-progress (2) –progress-interval. The user can control the progress indicator by using “--show-progress” option in any of the MEB operations. This option instructs MEB to output periodically short reports on the progress of time-consuming commands. The argument of this option instructs where the output could be sent. For example it could be stderr, stdout, file, fifo and table. With the “--show-progress” option both the total size of the backup to be copied and the size that’s already copied will be shown. Along with this, the state of the operation for example data or meta-data being copied or tables being locked and other such operations will also be reported. This gives more clear information to the DBA on the progress of the backup that’s happening. Interval between progress report in seconds is controlled by “--progress-interval” option. For more information on this please refer progress-report-options. MEB can also be accessed through GUI from MySQL WorkBench’s next version. This can be used as the front end interface for MEB users to perform backup operations at the click of a button. This feature was highly requested by DBAs and will be very useful. Refer http://insidemysql.com/mysql-workbench-6-0-a-sneak-preview/ for WorkBench upcoming release info. Along with the progress report feature some of the important issues like below are also addressed in MEB 3.8.2. In MEB 3.8.2 a new command line option “--on-disk-full” is introduced to abort or warn the user when a backup process encounters a full disk condition. When no option is given, by default it would abort. A few issues related to “incremental-backup” are also addressed in this release. Please refer 3.8.2 documentation for more details. It would be good for MEB users to move to 3.8.2 to take incremental backups. Overall the added usability and the important defects fixed in this release makes MySQL Enterprise Backup 3.8.2 a promising release.  

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• How to optimize mysql databse for serving 1000s of requests at a time ?

  - by Bilal

  How to optimize mysql databse for serving 1000s of requests at a time ? for a site like: linksnappy.com Is it possible to configure 2 seperate mysql servers into one load balancing server? like if one of them is overloaded switch to the next one ? same question for the http requests handling server. Another question : what kind of server do I need to server 1000s of requests at a time ? (http server) you can see the kind of site Im talking about is a download site. the server just dies when we have too many download requests. we currently have intel xeon quad core 2.4ghz with 4gb of ram.

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• SQL SERVER – Weekly Series – Memory Lane – #004

  - 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 Auto Generate Script to Delete Deprecated Fields in Current Database In early career everytime I have to drop a column, I had hard time doing it because I was scared what if that column was needed somewhere in the code. Due to this fear I never dropped any column. I just renamed the column. If the column which I renamed was needed afterwards it was very easy to rename it back again. However, it is not recommended to keep the deleted column renamed in the database. At every interval I used to drop the columns which was prefixed with specific word. This script is 6 years old but still works. Give it a look, I am open for improvements. 2007 Shrinking Truncate Log File – Log Full – Part 2 Shrinking database or mdf file is indeed bad thing and it creates lots of problems. However, once in a while there is legit requirement to shrink the log file – a very rare one. In the rare occasion shrinking or truncating the log file may be the only solution. However, one should make sure to take backup before and after the truncate or shrink as in case of a disaster they can be very useful. Remember that truncating log file will break the log chain and while restore it can create major issue. Anyway, use this feature with caution. 2008 Simple Use of Cursor to Print All Stored Procedures of Database Including Schema This is a very interesting requirement I used to face in my early career days, I needed to print all the Stored procedures of my database. Interesting enough I had written a cursor to do so. Today when I look back at this stored procedure, I believe there will be a much cleaner way to do the same task, however, I still use this SP quite often when I have to document all the stored procedures of my database. Interesting Observation about Order of Resultset without ORDER BY In industry many developers avoid using ORDER BY clause to display the result in particular order thinking that Index is enforcing the order. In this interesting example, I demonstrate that without using ORDER BY, same table and similar query can return different results. Query optimizer always returns results using any method which is optimized for performance. The learning is There is no order unless ORDER BY is used. 2009 Size of Index Table – A Puzzle to Find Index Size for Each Index on Table I asked this puzzle earlier where I asked how to find the Index size for each of the tables. The puzzle was very well received and lots of interesting answers were received. To answer this question I have written following blog posts. I suggest this weekend you try to solve this problem and see if you can come up with a better solution. If not, well here are the solutions. Solution 1 | Solution 2 | Solution 3 Understanding Table Hints with Examples Hints are options and strong suggestions specified for enforcement by the SQL Server query processor on DML statements. The hints override any execution plan the query optimizer might select for a query. The SQL Server Query optimizer is a very smart tool and it makes a better selection of execution plan. Suggesting hints to the Query Optimizer should be attempted when absolutely necessary and by experienced developers who know exactly what they are doing (or in development as a way to experiment and learn). Interesting Observation – TOP 100 PERCENT and ORDER BY I have seen developers and DBAs using TOP very causally when they have to use the ORDER BY clause. Theoretically, there is no need of ORDER BY in the view at all. All the ordering should be done outside the view and view should just have the SELECT statement in it. It was quite common that to save this extra typing by including ordering inside of the view. At several instances developers want a complete resultset and for the same they include TOP 100 PERCENT along with ORDER BY, assuming that this will simulate the SELECT statement with ORDER BY. 2010 SQLPASS Nov 8-11, 2010-Seattle – An Alternative Look at Experience In year 2010 I attended most prestigious SQL Server event SQLPASS between Nov 8-11, 2010 at Seattle. I have only one expression for the event - Best Summit Ever. Instead of writing about my usual routine or the event, I wrote about the interesting things I did and how I felt about it! When I go back and read it, I feel that this is the best event I attended in year 2010. Change Database Access to Single User Mode Using SSMS Image says all. 2011 SQL Server 2012 has introduced new analytic functions. These functions were long awaited and I am glad that they are now here. Before when any of this function was needed, people used to write long T-SQL code to simulate these functions. But now there’s no need of doing so. Having available native function also helps performance as well readability. Function SQLAuthority MSDN CUME_DIST CUME_DIST CUME_DIST FIRST_VALUE FIRST_VALUE FIRST_VALUE LAST_VALUE LAST_VALUE LAST_VALUE LEAD LEAD LEAD LAG LAG LAG PERCENTILE_CONT PERCENTILE_CONT PERCENTILE_CONT PERCENTILE_DISC PERCENTILE_DISC PERCENTILE_DISC PERCENT_RANK PERCENT_RANK PERCENT_RANK 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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• Encrypt connection between apache web server and mysql server.

  - by microchasm

  I'm setting up a local webapp. I have a CentOS-5 box that will be the webserver (Apache 2.2). I have another box (RHEL5) that will be used only for MySQL. The data will be encrypted on the webserver via PHP before being sent to the MySQL box and inserted into the db. All web-based connections to the webserver will be encrypted via SSL. From the research I've done, it's not totally clear on whether or not there is a need to encrypt the connection to the db from webserver (NB paranoia level: Orange). If it is not overkill, or even if it is (unless it is a really bad idea for some reason), any advice or pointers on the direction to take to get this done would be appreciated.

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• NetBeans, JSF, and MySQL Primary Keys using AUTO_INCREMENT

  - by MarkH

  I recently had the opportunity to spin up a small web application using JSF and MySQL. Having developed JSF apps with Oracle Database back-ends before and possessing some small familiarity with MySQL (sans JSF), I thought this would be a cakewalk. Things did go pretty smoothly...but there was one little "gotcha" that took more time than the few seconds it really warranted. The Problem Every DBMS has its own way of automatically generating primary keys, and each has its pros and cons. For the Oracle Database, you use a sequence and point your Java classes to it using annotations that look something like this: @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="POC_ID_SEQ") @SequenceGenerator(name="POC_ID_SEQ", sequenceName="POC_ID_SEQ", allocationSize=1) Between creating the actual sequence in the database and making sure you have your annotations right (watch those typos!), it seems a bit cumbersome. But it typically "just works", without fuss. Enter MySQL. Designating an integer-based field as PRIMARY KEY and using the keyword AUTO_INCREMENT makes the same task seem much simpler. And it is, mostly. But while NetBeans cranks out a superb "first cut" for a basic JSF CRUD app, there are a couple of small things you'll need to bring to the mix in order to be able to actually (C)reate records. The (RUD) performs fine out of the gate. The Solution Omitting all design considerations and activity (!), here is the basic sequence of events I followed to create, then resolve, the JSF/MySQL "Primary Key Perfect Storm": Fire up NetBeans. Create JSF project. Create Entity Classes from Database. Create JSF Pages from Entity Classes. Test run. Try to create record and hit error. It's a simple fix, but one that was fun to find in its completeness. :-) Even though you've told it what to do for a primary key, a MySQL table requires a gentle nudge to actually generate that new key value. Two things are needed to make the magic happen. First, you need to ensure the following annotation is in place in your Java entity classes: @GeneratedValue(strategy = GenerationType.IDENTITY) All well and good, but the real key is this: in your controller class(es), you'll have a create() function that looks something like this, minus the comment line and the setId() call in bold red type:     public String create() {         try {             // Assign 0 to ID for MySQL to properly auto_increment the primary key.             current.setId(0);             getFacade().create(current);             JsfUtil.addSuccessMessage(ResourceBundle.getBundle("/Bundle").getString("CategoryCreated"));             return prepareCreate();         } catch (Exception e) {             JsfUtil.addErrorMessage(e, ResourceBundle.getBundle("/Bundle").getString("PersistenceErrorOccured"));             return null;         }     } Setting the current object's primary key attribute to zero (0) prior to saving it tells MySQL to get the next available value and assign it to that record's key field. Short and simple…but not inherently obvious if you've never used that particular combination of NetBeans/JSF/MySQL before. Hope this helps! All the best, Mark

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• MySQL on Windows - how do I set the wait_timeout for connections using named pipes?

  - by gustafc

  I use a MySQL database running on a Windows box, and for performance reasons I'm connecting to it using named pipes. The (Java) application using the database (through Hibernate) can let the connection lie idle for quite a long time, which causes the connection to fail with the following message: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 33 558 297 milliseconds ago. The last packet sent successfully to the server was 33 558 297 milliseconds ago. is longer than the server configured value of 'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem. autoReconnect unfortunately has no effect (and neither does autoReconnectForPools), but the wait_timeout docs state that wait_timeout only applies "to TCP/IP and Unix socket file connections, not to connections made via named pipes, or shared memory". How can I change the wait_timeout for named pipes?

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• What possible events could cause a MySQL database to revert to a previous state?

  - by justkevin

  A client of mine recently had a strange event with their MySQL database. Several days ago, one database suddenly "went back in time". All the data was in the state it was in several months ago. Even most of the .MYD and .MYI files had timestamps from November. Fortunately, the server is not in production yet, but we need to understand how it happened so it doesn't happen again. I'm not a MySQL guru, but I couldn't think of a scenario that could cause the database to rewind like that short of restoring from a backup. What could have happened here? Where should I look for clues? (Server is FreeBSD 6.4)

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• How can I change my mysql user that has all privileges on a database to only have select privileges on one specific table?

  - by Glenn

  I gave my mysql user the "GRANT ALL PRIVILEGES ON database_name.* to my_user@localhost" treatment. Now I would like to be more granular, starting with lowering privileges on a specific table. I am hoping mysql has or can be set to follow a "least amount of privileges" policy, so I can keep the current setup and lower it for the one table. But I have not seen anything like this in the docs or online. Other than removing the DB level grant and re-granting on a table level, is there a way to get the same result by adding another rule?

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• Kostenlose MySQL Seminare im Mai

  - by A&C Redaktion

  Im Mai führen wir für Sie zahlreiche MySQL Seminare mit unterschiedlichen Themenschwerpunkten durch. Vom „Skalierbarkeitstag“ über einen praxisorienterten MySQL Enterprise Workshop bis hin zum Überblick über die Hochverfügbarkeitslösungen für MySQL mit Anwendungsbeispiel aus der Praxis. Wir würden uns sehr freuen, Sie bei einem dieser Seminare begrüßen zu dürfen. Die einzelnen Termine und Anmeldungslinks finden Sie hier. Wir freuen uns auf Ihre Teilnahme!

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• Linux: How to rename old mysqld when upgrading MySQL?

  - by Continuation

  I'm upgrading MySQL from MySQL 5.0 to Percona Server 5.1. I'm planning to just use yum remove and yum install to do the upgrade. However, I read in the documentation that it's a good idea to rename the old mysqld to mysqld-5.0. And if the upgrade doesn't work, I could just revert back to the old version. How exactly does this work? If I use yum remove, doesn't that mean the old mysqld is removed? So how do I rename it? Where is mysqld located? How do I find it? Thanks.

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• Prolog - How do you distinguish between just a string, and a variable? [closed]

  - by Mr Prolog

  When you are querying a Prolog database, often you will use terms that start with an uppercase letter as your variables. However, let's say that one of the constraints on your query is that a person's location must be "Dallas", and you want to query all the information in the database who meet those specifications. How would do you correctly make sure that Dallas is not interpreted as a variable to store a value in, and is interpreted as a string instead, for usage as a constraint on the query?

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• Open Source MariaDB, the MySQL fork to replace MySQL?

  - by Jenson

  Normal 0 false false false EN-GB X-NONE X-NONE MicrosoftInternetExplorer4 Frankly speaking, I’ve been out of touch with the Open source world for quite some time. Until recently, after I’ve joined the new government agency, I managed to do some research while given time to learn new technologies and languages. I started reading tech blogs and tech news again (since I’m not as busy as before where I need to rush for project deadlines in and out), and I spotted this MariaDB that really attracts my attention, this is the link to ZDNet article - http://www.zdnet.com/open-source-mariadb-a-mysql-fork-challenges-oracle-7000008311/ Open-Source MariaDB, a MySQL fork, challenges Oracle Yes, you’re right, MariaDB is a MySQL fork, and as mentioned in the article, MariaDB is run by the founder of MySQL, Michael ‘Monty’ Widenius, and he claims MariaDB is faster, more secure and has more features than MySQL. I’m actually very excited to know that the code is maintained by the same dedicated core team of MySQL in the past 18 years. They even bother to form a foundation, the MariaDB Foundation, to promote MariaDB. Already, there’s a lot of open source software officially supporting MariaDB, such as  Drupal, Jelastic – Java in the cloud, Kajona, MediaWiki, phpMyAdmin, Plone, SaltOs, WordPress, and Zend Framework. But the hosting service provider might not be readily supporting MariaDB in their hosting solution. Normal 0 false false false EN-GB X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-fareast-language:EN-US;} Time will tell whether MariaDB would be the real replacement for MySQL, I’m sorry I don’t think I should use alternative here ;-) For more information, please visit MariaDB official site. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-fareast-language:EN-US;}

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