- date 类型:
表示日期，格式类似这样: 000-00-00
- time 类型:
表示时间，格式类似这样: 00:00:00
- datetime 类型:
表示日期时间，格式类似这样: 0000-00-00 00:00:00
使用 now() 函数的时候，只有在当时执行的时候会获得当前时间，类似用于创建时间。
- timestamp 类型:
表示“时间戳”,其实就是一个整数数字，该数字是从是“时间起点”到现在为止的“秒数”。
“时间起点”是: 1970-1-1 0:0:0
timestamp 类型的字段，无需插入数据，而是会自动取得当前的日期时间(表示当前时刻)，类似用于修改时间或者最后一次更改内容时间。
而且，此类型字段会在数据被更新时，也同样自动取得当前的日期时间(表示修改的时刻)。
特别总结: 它在 insert 或 update 某行数据的时候，能够自动获得当前时间。
- year 类型:
- 表示年份，格式为:
0000
mysql> create table timeTest (t_time time, t_date date, t_datetime datetime, t_timestamp timestamp, t_year year); mysql> desc timeTest; +-------------+-----------+------+-----+-------------------+-----------------------------+ | Field | Type | Null | Key | Default | Extra | +-------------+-----------+------+-----+-------------------+-----------------------------+ | t_time | time | YES | | NULL | | | t_date | date | YES | | NULL | | | t_datetime | datetime | YES | | NULL | | | t_timestamp | timestamp | NO | | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP | | t_year | year(4) | YES | | NULL | | +-------------+-----------+------+-----+-------------------+-----------------------------+ mysql> insert into timeTest (t_time, t_date, t_datetime, t_timestamp, t_year) values ('10:57:50', '2018-7-29', '2008-8-8 20:00:00', '2018-7-29 11:00:12', 2020); mysql> select * from timeTest; +----------+------------+---------------------+---------------------+--------+ | t_time | t_date | t_datetime | t_timestamp | t_year | +----------+------------+---------------------+---------------------+--------+ | 10:57:50 | 2018-07-29 | 2008-08-08 20:00:00 | 2018-07-29 11:00:12 | 2020 | +----------+------------+---------------------+---------------------+--------+ mysql> insert into timeTest (t_time, t_date, t_datetime, t_year) values ('20:00:08', '2020-8-8', '2020-8-8 20:00:30', 2020); mysql> select * from timeTest; +----------+------------+---------------------+---------------------+--------+ | t_time | t_date | t_datetime | t_timestamp | t_year | +----------+------------+---------------------+---------------------+--------+ | 20:00:08 | 2020-08-08 | 2020-08-08 20:00:30 | 2020-07-06 13:42:56 | 2020 | +----------+------------+---------------------+---------------------+--------+ mysql> insert into timeTest (t_time, t_date, t_datetime, t_year) values ('20:00:08', '2020-8-8', now(), 2020); mysql> select * from timeTest; +----------+------------+---------------------+---------------------+--------+ | t_time | t_date | t_datetime | t_timestamp | t_year | +----------+------------+---------------------+---------------------+--------+ | 20:00:08 | 2020-08-08 | 2020-07-06 13:45:04 | 2020-07-06 13:45:04 | 2020 | +----------+------------+---------------------+---------------------+--------+ mysql> update timeTest set t_year=2021 where t_year=2020; mysql> select * from timeTest; +----------+------------+---------------------+---------------------+--------+ | t_time | t_date | t_datetime | t_timestamp | t_year | +----------+------------+---------------------+---------------------+--------+ | 20:00:08 | 2020-08-08 | 2020-08-08 20:00:30 | 2020-07-06 13:54:25 | 2021 | | 20:00:08 | 2020-08-08 | 2020-07-06 13:45:04 | 2020-07-06 13:54:25 | 2021 | +----------+------------+---------------------+---------------------+--------+
