[Oracle|MySQL]数据库时间类型

Oracle

SQL> select * from v$version;

BANNER
--------------------------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bi
PL/SQL Release 10.2.0.1.0 - Production
CORE    10.2.0.1.0      Production
TNS for Linux: Version 10.2.0.1.0 - Production
NLSRTL Version 10.2.0.1.0 - Production

1，date

如果字符串格式和NLS_DATE_FROMAT参数设置的时间格式相同，则不需进行转换，否则需要使用to_date函数进行格式转换

SQL> alter session set nls_date_format='yyyy-mm-dd hh24:mi:ss';

Session altered.

SQL> alter session set nls_date_language='american';

Session altered.

SQL> create table test(a date);

Table created.

SQL> insert into test values('2014-07-31 10:00:00');

1 row created.

SQL> insert into test values(to_date('201408','yyyymm'));

1 row created.

SQL> commit;

Commit complete.

SQL> select * from test;

A
-------------------
2014-07-31 10:00:00
2014-08-01 00:00:00

2，timestamp

Oracle中，timestamp类型除了精度可以达到毫秒级别之外，和date类型没有区别

 

MySQL

mysql> select version();
+-----------+
| version() |
+-----------+
| 5.6.12    |
+-----------+
1 row in set

如果字符串格式和系统设置的时间格式相同，则不需进行转换，否则需要使用str_to_date函数进行格式转换

mysql> create table test(date datetime);
Query OK, 0 rows affected

mysql> insert into test values('01-082014');
1292 - Incorrect datetime value: '01-082014' for column 'date' at row 1

mysql> insert into test values(str_to_date('01-082014','%d-%m%Y'));
Query OK, 1 row affected

mysql> select * from test;
+---------------------+
| date                |
+---------------------+
| 2014-08-01 00:00:00 |
+---------------------+
1 row in set

1，year

2，date

mysql> show variables where Variable_name = 'date_format';
+---------------+----------+
| Variable_name | Value    |
+---------------+----------+
| date_format   | %Y-%m-%d |
+---------------+----------+
1 row in set

3，time

mysql> show variables where Variable_name = 'time_format';
+---------------+----------+
| Variable_name | Value    |
+---------------+----------+
| time_format   | %H:%i:%s |
+---------------+----------+
1 row in set

4，datetime

mysql> show variables where Variable_name = 'datetime_format';
+-----------------+-------------------+
| Variable_name   | Value             |
+-----------------+-------------------+
| datetime_format | %Y-%m-%d %H:%i:%s |
+-----------------+-------------------+
1 row in set

5，timestamp

mysql> create table test(a timestamp, b timestamp);
Query OK, 0 rows affected

mysql> desc test;
+-------+-----------+------+-----+---------------------+-----------------------------+
| Field | Type      | Null | Key | Default             | Extra                       |
+-------+-----------+------+-----+---------------------+-----------------------------+
| a     | timestamp | NO   |     | CURRENT_TIMESTAMP   | on update CURRENT_TIMESTAMP |
| b     | timestamp | NO   |     | 0000-00-00 00:00:00 |                             |
+-------+-----------+------+-----+---------------------+-----------------------------+
2 rows in set

表中的第一个timestamp类型字段设有默认值，并且如果更新时不指定该字段的值，该字段的值会自动更新为CURRENT_TIMESTAMP()的值