DATE_ADD(date,INTERVAL expr unit), DATE_SUB(date,INTERVAL expr unit)
这些函数执行日期运算。日期是一个DATETIME或DATE值，指定起始日期。expr是一个表达式，指定要添加或从开始日期减去的间隔值。 expr是一个字符串;它可能会开始一个“ - ”的负区间值。unit是一个关键字，指示该单元中的表达应被解释。
INTERVAL关键字指定unit不区分大小写。
下表显示了expr参数的每个单位值的预期形式;
| unit 值 | 期望的 expr 格式 |
| MICROSECOND | MICROSECONDS |
| SECOND | SECONDS |
| MINUTE | MINUTES |
| HOUR | HOURS |
| DAY | DAYS |
| WEEK | WEEKS |
| MONTH | MONTHS |
| QUARTER | QUARTERS |
| YEAR | YEARS |
| SECOND_MICROSECOND | 'SECONDS.MICROSECONDS' |
| MINUTE_MICROSECOND | 'MINUTES.MICROSECONDS' |
| MINUTE_SECOND | 'MINUTES:SECONDS' |
| HOUR_MICROSECOND | 'HOURS.MICROSECONDS' |
| HOUR_SECOND | 'HOURS:MINUTES:SECONDS' |
| HOUR_MINUTE | 'HOURS:MINUTES' |
| DAY_MICROSECOND | 'DAYS.MICROSECONDS' |
| DAY_SECOND | 'DAYS HOURS:MINUTES:SECONDS' |
| DAY_MINUTE | 'DAYS HOURS:MINUTES' |
| DAY_HOUR | 'DAYS HOURS' |
| YEAR_MONTH | 'YEARS-MONTHS' |
QUARTER 值和WEEK可使用在MySQL5.0.0以上版本中。
mysql> SELECT DATE_ADD('1997-12-31 23:59:59', -> INTERVAL '1:1' MINUTE_SECOND); +---------------------------------------------------------+ | DATE_ADD('1997-12-31 23:59:59', INTERVAL... | +---------------------------------------------------------+ | 1998-01-01 00:01:00 | +---------------------------------------------------------+ 1 row in set (0.00 sec) mysql> SELECT DATE_ADD('1999-01-01', INTERVAL 1 HOUR); +---------------------------------------------------------+ | DATE_ADD('1999-01-01', INTERVAL 1 HOUR) | +---------------------------------------------------------+ | 1999-01-01 01:00:00 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
