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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, 5402👍, 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, 5396👍, 0💬

How To View User Privileges
How To View User Privileges? - MySQL FAQs - Managing User Accounts and Access Privileges If a regular user wants to see his/her own granted privileges, he/she can use the "SHOW GRANTS" command. If the "root" user wants to see other user's granted privileges, he/she can use the "SHOW GRANTS FOR userN...
2007-05-10, 5385👍, 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, 5380👍, 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, 5380👍, 0💬

How To Include Comments in SQL Statements
How To Include Comments in SQL Statements? - MySQL FAQs - Introduction to SQL Basics If you want to include comments in a SQL statement, you can first enter "--", then enter your comment until the end of the line. The tutorial exercise below shows you some good examples: SELECT 'Hello world!' FROM D...
2007-05-11, 5372👍, 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, 5369👍, 0💬

How To Delete an Existing Rows in a Table
How To Delete an Existing Rows in a Table? - PHP Script Tips - Working with MySQL Database If you want to remove a row from a table, you can use the DELETE statement with a WHERE clause to identify the row. The following sample script deletes one row: &lt;?php include "mysql_connection.php"; $sq...
2007-04-14, 5366👍, 0💬

How To Start MySQL Server Daemon mysqld
How To Start MySQL Server Daemon mysqld? - MySQL FAQs - Server Daemon mysqld Administration There are a number of ways to start MySQL server daemon, mysqld: Double click on the file name, mysqld.exe, in a file explorer window. This is an easy way to start the server. But you will not be able to spec...
2007-05-11, 5363👍, 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, 5358👍, 0💬

How To Delete a User Account
How To Delete a User Account? - MySQL FAQs - Managing User Accounts and Access Privileges If you want to delete a user account, you can connect to the server as "root" and use the "DROP USER ..." command to delete a user account. The tutorial exercise below shows you a good example: >cd \mysql\bin >...
2007-05-10, 5356👍, 0💬

How To Write Date and Time Literals
How To Write Date and Time Literals? - MySQL FAQs - Introduction to SQL Date and Time Handling MySQL offers a number of formats for you to use to enter date and time literals: ANSI standard format: "YYYY-MM-DD HH:MM:SS". Non-standard limiters. Like: "YYYY/MM/DD HH^MM^SS" or "YYYY.MM.DD HH-MM-SS". No...
2007-05-11, 5352👍, 0💬

What Is a Result Set Object
What Is a Result Set Object? - MySQL FAQs - Managing Tables and Running Queries with PHP Scripts A result set object is a logical representation of data rows returned by mysql_query() function on SELECT statements. Every result set object has an internal pointer used to identify the current row in t...
2007-05-10, 5347👍, 0💬

How To Add a New Column to an Existing Table
How To Add a New Column to an Existing Table? - MySQL FAQs - Understanding SQL CREATE, ALTER and DROP Statements If you have an existing table with existing data rows, and want to add a new column to that table, you can use the "ALTER TABLE ... ADD COLUMN" statement. The tutorial script below shows ...
2007-05-11, 5343👍, 0💬

How To Turn on mysql Extension on the PHP Engine
How To Turn on mysql Extension on the PHP Engine? - MySQL FAQs - PHP Connections and Query Execution The "mysql" API extension is provided as "php_mysql.dll" for Windows system. Your PHP binary download package should have "php_mysql.dll" included. No need for another download. But you need to check...
2007-05-10, 5340👍, 0💬

How Many Ways to Get the Current Time
How Many Ways to Get the Current Time? - MySQL FAQs - Introduction to SQL Date and Time Handling There are 8 ways to get the current time: SELECT NOW() FROM DUAL; 2006-07-01 10:02:41 SELECT CURRENT_TIME() FROM DUAL; 10:02:58 SELECT SYSDATE() FROM DUAL; 2006-07-01 10:03:21 mysql> SELECT CURRENT_TIMES...
2007-05-11, 5328👍, 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, 5327👍, 0💬

How To Access MySQL Servers through Firewalls
How To Access MySQL Servers through Firewalls? - MySQL FAQs - PHP Connections and Query Execution If your MySQL server is provided by an Internet service company, connecting to the server from your local machine will not be so easy, because there are firewalls between your local machine and your MyS...
2007-05-10, 5322👍, 0💬

What Happens If NULL Values Are Involved in Expressions
What Happens If NULL Values Are Involved in Expressions? - MySQL FAQs - Introduction to SQL Basics If NULL values are used in expressions, the resulting values will be NULL values. In other words: Arithmetic expressions with NULL values result NULL values. Comparison expressions with NULL values res...
2007-05-11, 5320👍, 0💬

What Are Numeric Data Types
What Are Numeric Data Types? - MySQL FAQs - Introduction to SQL Basics MySQL supports the following numeric data types: BIT(n) - An integer with n bits. BOOL same as BOOLEAN - Boolean values stored in 1 bit. TINYINT - A small integer stored in 1 byte. SMALLINT - A small integer stored in 2 bytes. ME...
2007-05-11, 5310👍, 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, 5304👍, 0💬

What Are NULL Values
What Are NULL Values? - MySQL FAQs - Introduction to SQL Basics NULL is a special value that represents no value. Here are basic rules about NULL values: NULL presents no value. NULL is not the same as an empty string ''. NULL is not the same as a zero value 0. NULL can be used as any data type. NUL...
2007-05-11, 5295👍, 0💬

How To Turn on Error Logs
How To Turn on Error Logs? - MySQL FAQs - Server Daemon mysqld Administration If you want MySQL to write critical errors into a log file, you can use the "--log-error=fileName" option at the "mysqld" command line. The tutorial exercise below shows you a good example on how to use this option: >cd \m...
2007-05-11, 5290👍, 0💬

How To Turn on Query Logs
How To Turn on Query Logs? - MySQL FAQs - Server Daemon mysqld Administration If you want MySQL to write query logs to a file, you can use the "--log=fileName" option at the "mysqld" command line. The tutorial exercise below shows you a good example on how to use this option and view the query log f...
2007-05-11, 5290👍, 0💬

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