IF

Description

The IF() function returns a value if a condition is TRUE, or another value if a condition is FALSE.

Syntax

  1. > IF(expr1,expr2,expr3)

  • If expr1 is TRUE (expr1 <> 0 and expr1 IS NOT NULL), IF() returns expr2. Otherwise, it returns expr3.

  • If only one of expr2 or expr3 is explicitly NULL, the result type of the IF() function is the type of the non-NULL expression.

  • The default return type of IF() (which may matter when it is stored into a temporary table) is calculated as follows:

    • If expr2 or expr3 produce a string, the result is a string.

    • If expr2 and expr3 are both strings, the result is case-sensitive if either string is case-sensitive.

    • If expr2 or expr3 produce a floating-point value, the result is a floating-point value.

    • If expr2 or expr3 produce an integer, the result is an integer.

Examples

  1. mysql> SELECT IF(1>2,2,3);
  2. +-----------------+
  3. | if(1 > 2, 2, 3) |
  4. +-----------------+
  5. |               3 |
  6. +-----------------+
  7. 1 row in set (0.01 sec)
  8. mysql> SELECT IF(1<2,'yes','no');
  9. +--------------------+
  10. | if(1 < 2, yes, no) |
  11. +--------------------+
  12. | yes                |
  13. +--------------------+
  14. 1 row in set (0.00 sec)
  1. CREATE TABLE t1 (st varchar(255) NOT NULL, u int(11) NOT NULL);
  2. INSERT INTO t1 VALUES ('a',1),('A',1),('aa',1),('AA',1),('a',1),('aaa',0),('BBB',0);
  4. mysql> select if(u=1,st,st) s from t1 order by s;
  5. +------+
  6. | s    |
  7. +------+
  8. | A    |
  9. | AA   |
  10. | BBB  |
  11. | a    |
  12. | a    |
  13. | aa   |
  14. | aaa  |
  15. +------+
  16. 7 rows in set (0.00 sec)
  18. mysql> select if(u=1,st,st) s from t1 where st like "%a%" order by s;
  19. +------+
  20. | s    |
  21. +------+
  22. | a    |
  23. | a    |
  24. | aa   |
  25. | aaa  |
  26. +------+
  27. 4 rows in set (0.00 sec)

Constraints

Parameters BIGINT and VARCHAR are not supported with the function ‘if’.