mysql查询两个日期之间相差多少天?

需求描述:

　　在mysql中,查看两个日期之间相差多少天

操作过程:

1.通过datediff函数,查看两个日期之间相差多少天

mysql> select datediff('2018-06-26','2018-06-25'),datediff('2018-06-20','2018-06-26');
+-------------------------------------+-------------------------------------+
| datediff('2018-06-26','2018-06-25') | datediff('2018-06-20','2018-06-26') |
+-------------------------------------+-------------------------------------+
|                                   1 |                                  -6 |
+-------------------------------------+-------------------------------------+
1 row in set (0.00 sec)

备注:datediff(expr1,expr2),一般返回的就是expr1-expr2的差值,结果可以是正数,也可以是负数.主要是两个日期之间相差多少天.

2.带有时分秒的表达式

mysql> select datediff('2018-06-26 22:00:00','2018-06-25'),datediff('2018-06-20','2018-06-26 21:00:00');
+----------------------------------------------+----------------------------------------------+
| datediff('2018-06-26 22:00:00','2018-06-25') | datediff('2018-06-20','2018-06-26 21:00:00') |
+----------------------------------------------+----------------------------------------------+
|                                            1 |                                           -6 |
+----------------------------------------------+----------------------------------------------+
1 row in set (0.00 sec)

备注:在日期计算中,如果存在时分秒的部分,是会被忽略的只对日期的部分进行计算即只对天计算.

文档创建时间:2018年6月26日12:47:32

官方文档参考:

DATEDIFF(expr1,expr2)
 
DATEDIFF() returns expr1 − expr2 expressed as a value in days from one date to the other. expr1 and expr2 are date or date-and-time expressions.
Only the date parts of the values are used in the calculation.
 
mysql> SELECT DATEDIFF('2007-12-31 23:59:59','2007-12-30');
        -> 1
mysql> SELECT DATEDIFF('2010-11-30 23:59:59','2010-12-31');
        -> -31