Example
Compare two expressions:
SELECT NULLIF(25, 25);
Definition and Usage
The NULLIF() function compares two expressions and returns NULL if they are equal. Otherwise, the first expression is returned.
Syntax
NULLIF(expr1, expr2)
Author: Mostafa
MySQL LAST_INSERT_ID Function
Example
Return the AUTO_INCREMENT id of the last row that has been inserted in a table:
SELECT LAST_INSERT_ID();
Definition and Usage
The LAST_INSERT_ID() function returns the AUTO_INCREMENT id of the last row that has been inserted in a table.
Syntax
LAST_INSERT_ID(expression)
MySQL ISNULL Function
Example
Test whether an expression is NULL:
SELECT ISNULL(NULL);
Definition and Usage
The ISNULL() function returns 1 or 0 depending on whether an expression is NULL.
If expression is NULL, this function returns 1. Otherwise, it returns 0.
Syntax
ISNULL(expression)
MySQL IFNULL Function
Example
Return the specified value IF the expression is NULL, otherwise return the expression:
SELECT IFNULL(NULL, "Iampsp.com");
Definition and Usage
The IFNULL() function returns a specified value if the expression is NULL.
If the expression is NOT NULL, this function returns the expression.
Syntax
IFNULL(expression, alt_value)
MySQL IF Function
Example
Return “YES” if the condition is TRUE, or “NO” if the condition is FALSE:
SELECT IF(500<1000, "YES", "NO");
Definition and Usage
The IF() function returns a value if a condition is TRUE, or another value if a condition is FALSE.
Syntax
IF(condition, value_if_true, value_if_false)
MySQL DATABASE Function
Example
Return the name of the current (default) database:
SELECT DATABASE();
Definition and Usage
The DATABASE() function returns the name of the current database.
If there is no current database, this function returns NULL or “”.
Syntax
DATABASE()
MySQL CURRENT_USER Function
Example
Return the user name and host name for the MySQL account:
SELECT CURRENT_USER();
Definition and Usage
The CURRENT_USER() function returns the user name and host name for the MySQL account that the server used to authenticate the current client.
The result is returned as a string in the UTF8 character set.
Syntax
CURRENT_USER()
MySQL CONVERT Function
Example
Convert a value to a DATE datatype:
SELECT CONVERT("2017-08-29", DATE);
Definition and Usage
The CONVERT() function converts a value into the specified datatype or character set.
Syntax
CONVERT(value, type)
OR:
CONVERT(value USING charset)
MySQL CONV Function
Example
Convert a number from numeric base system 10 to numeric base system 2:
SELECT CONV(15, 10, 2);
Definition and Usage
The CONV() function converts a number from one numeric base system to another, and returns the result as a string value.
Note: This function returns NULL if any of the parameters are NULL.
Syntax
CONV(number, from_base, to_base)
MySQL CONNECTION_ID Function
Example
Return the unique connection ID for the current connection:
SELECT CONNECTION_ID();
Definition and Usage
The CONNECTION_ID() function returns the unique connection ID for the current connection.
Syntax
CONNECTION_ID()