日期类型

DATE TIME DATETIME TIMESTAMP YEAR

作用:存储用户注册时间,文章发布时间,员工入职时间,出生时间,过期时间等

        YEAR
YYYY(1901/2155) DATE
YYYY-MM-DD(1000-01-01/9999-12-31) TIME
HH:MM:SS('-838:59:59'/'838:59:59') DATETIME YYYY-MM-DD HH:MM:SS(1000-01-01 00:00:00/9999-12-31 23:59:59 Y) TIMESTAMP YYYYMMDD HHMMSS(1970-01-01 00:00:00/2037 年某时)

验证

============year===========
MariaDB [db1]> create table t10(born_year year); #无论year指定何种宽度,最后都默认是year(4)
MariaDB [db1]> insert into t10 values
-> (1900),
-> (1901),
-> (2155),
-> (2156);
MariaDB [db1]> select * from t10;
+-----------+
| born_year |
+-----------+
| 0000 |
| 1901 |
| 2155 |
| 0000 |
+-----------+ ============date,time,datetime===========
MariaDB [db1]> create table t11(d date,t time,dt datetime);
MariaDB [db1]> desc t11;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| d | date | YES | | NULL | |
| t | time | YES | | NULL | |
| dt | datetime | YES | | NULL | |
+-------+----------+------+-----+---------+-------+ MariaDB [db1]> insert into t11 values(now(),now(),now());
MariaDB [db1]> select * from t11;
+------------+----------+---------------------+
| d | t | dt |
+------------+----------+---------------------+
| 2017-07-25 | 16:26:54 | 2017-07-25 16:26:54 |
+------------+----------+---------------------+ ============timestamp===========
MariaDB [db1]> create table t12(time timestamp);
MariaDB [db1]> insert into t12 values();
MariaDB [db1]> insert into t12 values(null);
MariaDB [db1]> select * from t12;
+---------------------+
| time |
+---------------------+
| 2017-07-25 16:29:17 |
| 2017-07-25 16:30:01 |
+---------------------+ ============注意啦,注意啦,注意啦===========
1. 单独插入时间时,需要以字符串的形式,按照对应的格式插入
2. 插入年份时,尽量使用4位值
3. 插入两位年份时,<=69,以20开头,比如50, 结果2050
>=70,以19开头,比如71,结果1971
MariaDB [db1]> create table t12(y year);
MariaDB [db1]> insert into t12 values
-> (50),
-> (71);
MariaDB [db1]> select * from t12;
+------+
| y |
+------+
| 2050 |
| 1971 |
+------+ ============综合练习===========
MariaDB [db1]> create table student(
-> id int,
-> name varchar(20),
-> born_year year,
-> birth date,
-> class_time time,
-> reg_time datetime); MariaDB [db1]> insert into student values
-> (1,'alex',"1995","1995-11-11","11:11:11","2017-11-11 11:11:11"),
-> (2,'egon',"1997","1997-12-12","12:12:12","2017-12-12 12:12:12"),
-> (3,'wsb',"1998","1998-01-01","13:13:13","2017-01-01 13:13:13"); MariaDB [db1]> select * from student;
+------+------+-----------+------------+------------+---------------------+
| id | name | born_year | birth | class_time | reg_time |
+------+------+-----------+------------+------------+---------------------+
| 1 | alex | 1995 | 1995-11-11 | 11:11:11 | 2017-11-11 11:11:11 |
| 2 | egon | 1997 | 1997-12-12 | 12:12:12 | 2017-12-12 12:12:12 |
| 3 | wsb | 1998 | 1998-01-01 | 13:13:13 | 2017-01-01 13:13:13 |
+------+------+-----------+------------+------------+---------------------+

datetime与timestamp的区别

在实际应用的很多场景中,MySQL的这两种日期类型都能够满足我们的需要,存储精度都为秒,但在某些情况下,会展现出他们各自的优劣。
下面就来总结一下两种日期类型的区别。 1.DATETIME的日期范围是1001——9999年,TIMESTAMP的时间范围是1970——2038年。 2.DATETIME存储时间与时区无关,TIMESTAMP存储时间与时区有关,显示的值也依赖于时区。在mysql服务器,
操作系统以及客户端连接都有时区的设置。 3.DATETIME使用8字节的存储空间,TIMESTAMP的存储空间为4字节。因此,TIMESTAMP比DATETIME的空间利用率更高。 4.DATETIME的默认值为null;TIMESTAMP的字段默认不为空(not null),默认值为当前时间(CURRENT_TIMESTAMP),
如果不做特殊处理,并且update语句中没有指定该列的更新值,则默认更新为当前时间。
05-17 22:04