Mysql 条件函数 If Ifnull

September 21, 2015

IF

IF(condition,true-value,false-value)

IFNULL

IFNULL(cloumn-name, true-value)

与NULL比较

IS NULL IS NOT NUL <=>

1

SELECT name, IF(id IS NULL, ‘Unknown’,id) as ‘id’ FROM taxpayer;