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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, 5087👍, 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, 5085👍, 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, 5083👍, 0💬

How To Use Regular Expression in Pattern Match Conditions
How To Use Regular Expression in Pattern Match Conditions? - MySQL FAQs - Introduction to SQL Basics If you have a pattern that is too complex for LIKE to handle, you can use the regular expression pattern condition: REGEXP. The following tutorial exercise provides you some good examples: SELECT 'FY...
2007-05-11, 5081👍, 0💬

How To Name Query Output Columns
How To Name Query Output Columns? - MySQL FAQs - SQL SELECT Statements with JOIN and Subqueries Each column in the query output has a default name. If you don't like the default name, you can specify a new name for any column in the query output by using the AS clause. The following statement shows ...
2007-05-11, 5072👍, 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, 5072👍, 0💬

What Are the Differences between CHAR and VARCHAR
What Are the Differences between CHAR and VARCHAR? - MySQL FAQs - Introduction to SQL Basics CHAR and VARCHAR are both ASCII character data types by default. But they have the following major differences: CHAR stores values in fixed lengths. Values are padded with space characters to match the speci...
2007-05-11, 5069👍, 0💬

What Are the Predefined User Accounts
What Are the Predefined User Accounts? - MySQL FAQs - Managing User Accounts and Access Privileges There is only one predefined user account called "root": "root" was created during the installation process. "root" has no password initially. You need to assign a new password as soon as you finishes ...
2007-05-10, 5069👍, 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, 5055👍, 0💬

How To Create a New View
How To Create a New View? - MySQL FAQs - Understanding SQL CREATE, ALTER and DROP Statements You can create a new view based on one or more existing tables by using the "CREATE VIEW viewName AS selectStatement" statement as shown in the following script: mysql> CREATE TABLE comment (faqID INTEGER, m...
2007-05-11, 5050👍, 0💬

How To Write a Query with a Right Outer Join
How To Write a Query with a Right Outer Join? - MySQL FAQs - SQL SELECT Statements with JOIN and Subqueries If you want to query from two tables with a right outer join, you can use the RIGHT OUTER JOIN ... ON clause in the FROM clause. The following query returns output with a right outer join from...
2007-05-11, 5048👍, 0💬

What Are Date and Time Intervals
What Are Date and Time Intervals? - MySQL FAQs - Introduction to SQL Date and Time Handling A date and time interval is special value to be used to increment or decrement a date or a time at a given date or time unit. A data and time interval should be expression in the format of "INTERVAL expressio...
2007-05-11, 5048👍, 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, 5046👍, 0💬

How To Define and Use Table Alias Names
How To Define and Use Table Alias Names? - MySQL FAQs - SQL SELECT Statements with JOIN and Subqueries When column names need to be prefixed with table names, you can define table alias name and use them to prefix column names as shown in the following select statement: mysql> SELECT l.id, l.url, r....
2007-05-11, 5044👍, 0💬

How To Use Existing Values in UPDATE Statements
How To Use Existing Values in UPDATE Statements? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If a row matches the WHERE clause in a UPDATE statement, existing values in this row can be used in expressions to provide new values in the SET clause. Existing values are represen...
2007-05-11, 5041👍, 0💬

How To Query Multiple Tables Jointly
How To Query Multiple Tables Jointly? - PHP Script Tips - Working with MySQL Database If you want to query information stored in multiple tables, you can use the SELECT statement with a WHERE condition to make an inner join. Assuming that you have 3 tables in a forum system: "users" for user profile...
2007-04-19, 5038👍, 0💬

What Are the Differences between BINARY and VARBINARY
What Are the Differences between BINARY and VARBINARY? - MySQL FAQs - Introduction to SQL Basics Both BINARY and VARBINARY are both binary byte data types. But they have the following major differences: BINARY stores values in fixed lengths. Values are padded with 0x00. VARBINARY stores values in va...
2007-05-11, 5025👍, 0💬

How To Check Server Status with "mysqladmin"
How To Check Server Status with "mysqladmin"? - MySQL FAQs - Administrator Tools for Managing MySQL Server If you want to check the server status by with "mysqladmin", you can following this tutorial example: >cd \mysql\bin >mysqladmin -u root status Uptime: 223 Threads: 1 Questions: 1 Slow queries:...
2007-05-11, 5024👍, 0💬

What Tools Available for Managing MySQL Server
What Tools Available for Managing MySQL Server? - MySQL FAQs - Administrator Tools for Managing MySQL Server MySQL comes with the following programs as administration tools for you to manage your MySQL server: mysqld - MySQL server daemon. You can use "mysqld" to start your MySQL server. mysqladmin ...
2007-05-11, 5021👍, 0💬

Can the Query Output Be Sorted by Multiple Columns
Can the Query Output Be Sorted by Multiple Columns? - MySQL FAQs - SQL SELECT Query Statements with GROUP BY You can specifying multiple columns in the ORDER BY clause as shown in the following example statement, which returns employees' salaries sorted by department and salary value: mysql> SELECT ...
2007-05-11, 5007👍, 0💬

What Are Date and Time Functions
What Are Date and Time Functions? - MySQL FAQs - Introduction to SQL Date and Time Handling MySQL offers a number of functions for date and time values: ADDDATE(date, INTERVAL expr unit) - Adding days to a date. Same as DATE_ADD(). ADDTIME(time1, time2) - Adding two time values together. CURDATE() -...
2007-05-11, 4999👍, 0💬

Is the Order of Columns in the SET Clause Important
Is the Order of Columns in the SET Clause Important? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements Yes. The order of columns in the SET clause of the UPDATE statement is important. There is a BIG DIFFERENCE between MySQL and Oracle on update columns with previous values: Orac...
2007-05-11, 4998👍, 0💬

Can Group Functions Be Used in the ORDER BY Clause
Can Group Functions Be Used in the ORDER BY Clause? - MySQL FAQs - SQL SELECT Query Statements with GROUP BY If the query output is aggregated as groups, you can sort the groups by using group functions in the ORDER BY clause. The following statement returns how many links were created in each year ...
2007-05-11, 4997👍, 0💬

What Are Storage Engines
What Are Storage Engines? - MySQL FAQs - Storage Engines: MyISAM, InnoDB and BDB Storage engines are programs that are integrated into MySQL database management system to manage data tables. MySQL 5.0 supports the following major storage engines: MyISAM Storage Engine - MySQL default storage engine....
2007-05-10, 4991👍, 0💬

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