创建数据库,创建表。
Sql代码
mysql> create database ssh2;
Query OK, 1 row affected (0.04 sec)
mysql> use ssh2;
Database changed
mysql> create table user(
-> id integer primary key,
-> firstname varchar(200) not null,
-> lastname varchar(200) not null,
-> age integer
-> );
Query OK, 0 rows affected (0.46 sec)
给主键增加一个自增的功能:
Java代码
mysql> alter table user modify id integer auto_increment ;
Query OK, 1 row affected (0.28 sec)
Records: 1 Duplicates: 0 Warnings: 0
这样,上面的user表里面的主键,id可以自增了。
给上面的主键id增加默认值和自增功能。
Java代码
mysql> alter table user modify id integer auto_increment ;
Query OK, 0 rows affected (0.39 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table user modify id integer default ‘1’;
Query OK, 0 rows affected (0.16 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table user modify id integer auto_increment ;
Query OK, 1 row affected (0.28 sec)
Records: 1 Duplicates: 0 Warnings: 0
MySql获取系统时间:
Java代码
mysql> alter table user add createtime timestamp default current_timestamp;
Query OK, 2 rows affected (0.17 sec)
Records: 2 Duplicates: 0 Warnings: 0
MySql设置主键不能为空,还要自动增长(这里没有设置默认值,但是默认是1,从1开始增长。),还要得到系统默认日期:
Java代码
mysql> create table dd(
-> id int primary key not null auto_increment,
-> name varchar(20),
-> time timestamp default current_timestamp
-> );
Query OK, 0 rows affected (0.10 sec)
mysql> insert into dd(name) values (‘fhihgifds’);
Query OK, 1 row affected (0.14 sec)
mysql> insert into dd(name) values (‘steven’);
Query OK, 1 row affected (0.08 sec)
mysql> select * from dd;
+—-+———–+———————+
| id | name | time |
+—-+———–+———————+
| 1 | fhihgifds | 2011-03-27 01:58:46 |
| 2 | steven | 2011-03-27 01:59:35 |
+—-+———–+———————+
2 rows in set (0.08 sec)
mysql> insert into dd(name) values (‘anthony’);
Query OK, 1 row affected (0.09 sec)
mysql> select * from dd;
+—-+———–+———————+
| id | name | time |
+—-+———–+———————+
| 1 | fhihgifds | 2011-03-27 01:58:46 |
| 2 | steven | 2011-03-27 01:59:35 |
| 3 | anthony | 2011-03-27 02:00:07 |
+—-+———–+———————+
3 rows in set (0.00 sec)
mysql>
尘影 2022-6-180
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很有帮助