MySQL的Data_ADD函数与日期格式化函数说明_MySQL
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- DATE_ADD(date,INTERVAL expr type) DATE_SUB(date,INTERVAL expr type)
这些函数执行日期运算。 date 是一个 DATETIME 或DATE值，用来指定起始时间。 expr 是一个表达式，用来指定从起始日期添加或减去的时间间隔值。 Expr是一个字符串;对于负值的时间间隔，它可以以一个 ‘-'开头。 type 为关键词，它指示了表达式被解释的方式。
关键词INTERVA及 type 分类符均不区分大小写。
以下表显示了type 和expr 参数的关系：
type 值 |
预期的 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' |
MySQL 允许任何expr 格式中的标点分隔符。表中所显示的是建议的 分隔符。若 date 参数是一个 DATE 值，而你的计算只会包括 YEAR、MONTH和DAY部分(即, 没有时间部分), 其结果是一个DATE 值。否则，结果将是一个 DATETIME值。
若位于另一端的表达式是一个日期或日期时间值 ， 则INTERVAL expr type只允许在 + 操作符的两端。对于
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