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What Is Union
What Is Union? - MySQL FAQs - Database Basics and Terminologies Join is data retrieval operation that combines multiple query outputs of the same structure into a single output.
2007-05-10, 4938👍, 0💬

What Is Index
What Is Index? - MySQL FAQs - Database Basics and Terminologies An index is a single column or multiple columns defined to have values pre-sorted to speed up data retrieval speed.
2007-05-10, 4931👍, 0💬

How To Find Out the Current Transaction Mode
How To Find Out the Current Transaction Mode? - MySQL FAQs - Transaction Management: Commit or Rollback If you are not sure about your current transaction mode, you can use the "SELECT @@AUTOCOMMIT FROM DUAL" statement to find out as shown in the following tutorial exercise: >\mysql\bin\mysql -u dev...
2007-05-11, 4915👍, 0💬

What Happens to the Current Transaction If the Session Is Killed
What Happens to the Current Transaction If the Session Is Killed? - MySQL FAQs - Transaction Management: Commit or Rollback If a session is killed by the DBA, the current transaction in that session will be rolled back and ended. All the database changes made in the current transaction will be remov...
2007-05-11, 4913👍, 0💬

How To Connect to a MySQL Sever with a Port Number
How To Connect to a MySQL Sever with a Port Number? - MySQL FAQs - PHP Connections and Query Execution If you want to connect a MySQL server with a non-default port number, you need to use the "mysql_connect($server)" function with $server in the format of "hostName:portNubmber". The tutorial exerci...
2007-05-10, 4912👍, 0💬

How To Calculate the Difference between Two Time Values
How To Calculate the Difference between Two Time Values? - MySQL FAQs - Introduction to SQL Date and Time Handling If you have two time values, and you want to know the time difference between them, you can use the TIMEDIFF(time1, time2) function as shown below: SELECT TIMEDIFF(TIME('19:26:50'), TIM...
2007-05-11, 4908👍, 0💬

What Happens If the UPDATE Subquery Returns No Rows
What Happens If the UPDATE Subquery Returns No Rows? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If you use a subquery to assign new values in the SET clause in an UPDATE statement, and the subquery returns no rows for an outer row, MySQL will provide a NULL value to the SE...
2007-05-11, 4900👍, 0💬

How To Get a List of Databases from MySQL Servers
How To Get a List of Databases from MySQL Servers? - MySQL FAQs - PHP Connections and Query Execution Once you got a MySQL server connection object successfully, you need to know what databases are available on the server and which database you should use to manage your tables and data. To get a lis...
2007-05-10, 4899👍, 0💬

How To Turn on Binary Logs
How To Turn on Binary Logs? - MySQL FAQs - Server Daemon mysqld Administration If you want MySQL to write binary logs to a file, you can use the "--log-bin=fileBaseName" option at the "mysqld" command line. The tutorial exercise below shows you a good example on how to use this option: >cd \mysql\bi...
2007-05-11, 4897👍, 0💬

What Happens If Unique Value Constraints Are Violated
What Happens If Unique Value Constraints Are Violated? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If you are inserting a new record that has values violating a unique constraint, you will get an error. Note that primary key column has a unique value constraint by default. ...
2007-05-11, 4892👍, 0💬

What Is "mysqlcheck"
What Is "mysqlcheck"? - MySQL FAQs - Administrator Tools for Managing MySQL Server "mysqlcheck" is a command-line interface for administrators to check and repair tables. Here are some sample commands supported by "mysqlcheck": "mysqlcheck databaseName tableName" - Checks the specified table in the ...
2007-05-11, 4891👍, 0💬

How To Commit the Current Transaction
How To Commit the Current Transaction? - MySQL FAQs - Transaction Management: Commit or Rollback If you have used some DML statements updated some data objects, and you want to have the updates to be permanently recorded in the database, you can use the COMMIT command. It will make all the database ...
2007-05-11, 4889👍, 0💬

What Is Column
What Is Column? - MySQL FAQs - Database Basics and Terminologies A column defines one piece of data stored in all rows of the table.
2007-05-10, 4887👍, 0💬

How To Use SELECT Statement to Count the Number of Rows
How To Use SELECT Statement to Count the Number of Rows? - MySQL FAQs - SQL SELECT Query Statements with GROUP BY If you want to count the number of rows, you can use the COUNT(*) function in the SELECT clause. The following tutorial exercise shows you some good example: mysql> SELECT COUNT(*) FROM ...
2007-05-11, 4881👍, 0💬

How To Include Character Strings in SQL statements
How To Include Character Strings in SQL statements? - MySQL FAQs - Introduction to SQL Basics If you want to include character strings in your SQL statements, you need to quote them in one of the following formats: Using single quotes. For example 'FYIcenter.com'. Using double quotes. For example "F...
2007-05-11, 4880👍, 0💬

How To Experiment Dead Locks
How To Experiment Dead Locks? - MySQL FAQs - Transaction Management: Commit or Rollback If you want to have some experience with dead locks, you can create two windows running two mysql transactions in two sessions at the REPEATABLE READ transaction isolation level. Then run some UPDATE statements a...
2007-05-09, 4872👍, 0💬

How To Get the Number of Rows Selected or Affected by a SQL Statement
How To Get the Number of Rows Selected or Affected by a SQL Statement? - MySQL FAQs - Managing Tables and Running Queries with PHP Scripts There are two functions you can use the get the number of rows selected or affected by a SQL statement: mysql_num_rows($res) - Returns the number of rows selecte...
2007-05-10, 4869👍, 0💬

What Is "mysqladmin"
What Is "mysqladmin"? - MySQL FAQs - Administrator Tools for Managing MySQL Server "mysqladmin" is a command-line interface for administrators to perform server administration tasks. It support a number of commonly used commands like: "mysqladmin shutdown" - Shuts down the server. "mysqladmin ping" ...
2007-05-11, 4865👍, 0💬

What Are Transaction Isolation Levels
What Are Transaction Isolation Levels? - MySQL FAQs - Transaction Management: Commit or Rollback There are 4 transaction isolation levels defined by SQL-1992 standard: READ UNCOMMITTED - The SELECT statements in one transaction will read uncommitted data changes from transactions of all connected se...
2007-05-09, 4861👍, 0💬

How To Count Duplicated Values in a Column
How To Count Duplicated Values in a Column? - MySQL FAQs - SQL SELECT Query Statements with GROUP BY If you have a column with duplicated values, and you want to know what are those duplicated values are and how many duplicates are there for each of those values, you can use the GROUP BY ... HAVING ...
2007-05-11, 4853👍, 0💬

What Is Row
What Is Row? - MySQL FAQs - Database Basics and Terminologies A row is a unit of data with related data items stored as one item in one column in a table.
2007-05-10, 4853👍, 0💬

How To Properly Shutdown MySQL Server Daemon mysqld
How To Properly Shutdown MySQL Server Daemon mysqld? - MySQL FAQs - Server Daemon mysqld Administration The proper way to shutdown your MySQL server is to the use "mysqladmin shutdown" command. Other ways to shutdown your server include: Enter "mysqladmin -u root -ppassowrd shutdown" command with op...
2007-05-11, 4846👍, 0💬

What Happens If the UPDATE Subquery Returns Multiple Rows
What Happens If the UPDATE Subquery Returns Multiple Rows? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If a subquery is used in a UPDATE statement, it must return exactly one row for each row in the update table that matches the WHERE clause. If it returns multiple rows, My...
2007-05-11, 4844👍, 0💬

What Are the Impacts on Applications from Locks, Timeouts, and DeadLocks
What Are the Impacts on Applications from Locks, Timeouts, and DeadLocks? - MySQL FAQs - Transaction Management: Commit or Rollback If you are using transactions with REPEATABLE READ isolation level and transaction safe storage engines in your applications, data locks, lock timeouts, and dead lock d...
2007-05-08, 4835👍, 0💬

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