PHP & MySQL: Novice to Ninja, 5th Edition

Appendix C. MySQL Functions

MySQL provides a sizeable library of functions to format and combine data within SQL queries in order to produce the desired results in the preferred format. This appendix provides a reference to the most useful of these functions, as implemented in MySQL as of version 5.5.22 (current this writing).

For a complete, up-to-date reference to supported SQL functions, see the MySQL Reference Manual.

Control Flow Functions

IFNULL(expr1, expr2)

This function returns expr1 unless it’s NULL, in which case it returns expr2.

NULLIF(expr1, expr2)

This function returns expr1 unless it equals expr2, in which case it returns NULL.

IF(expr1, expr2, expr3)

If expr1 is TRUE (that is, not NULL or 0), this function returns expr2; otherwise, ...