MySQL process control IF(), IFNULL(), NULLIF(), ISNULL() functions

In MySQL, you can use IF(), IFNULL(), NULLIF(), and ISNULL() functions to control the process.

1. Use of IF() function

IF(expr1,expr2,expr3) returns the value of expr2 if expr1 is true, and returns the value of expr3 if expr1 is false.

SELECT IF(TRUE,'A','B'); -- Output: A
SELECT IF(FALSE,'A','B'); -- Output: B

2. Use of IFNULL() function

IFNULL(expr1,expr2) returns the value of expr2 if the value of expr1 is null, and returns the value of expr1 if the value of expr1 is not null.

SELECT IFNULL(NULL,'B'); -- Output: B
SELECT IFNULL('HELLO','B'); -- Output: HELLO

3. Use of NULLIF() function

NULLIF(expr1,expr2) , if expr1=expr2, then the return value is null, otherwise the return value is the value of expr1.

SELECT NULLIF('A','A'); -- Output: null
SELECT NULLIF('A','B'); -- Output: A

4. Use of ISNULL() function

ISNULL(expr) returns 1 if the value of expr is null, and returns 0 if the value of expr1 is not null.

SELECT ISNULL(NULL); -- Output: 1
SELECT ISNULL('HELLO'); -- Output: 0

The above is the introduction of the use of MySQL process control IF(), IFNULL(), NULLIF(), and ISNULL() functions. I hope it will be helpful to you. I would also like to thank everyone for their support of the 123WORDPRESS.COM website!