創建表
create table 表名
create table if not exists 表名
mysql> create database company;
Query OK, 1 row affected (0.00 sec)
mysql> use company;
Database changed
mysql> create table if not exists t_dept(
-> deptno int,
-> dname varchar(20),
-> loc varchar(40));
Query OK, 0 rows affected (0.20 sec)
mysql> show tables;
+-------------------+
| Tables_in_company |
+-------------------+
| t_dept |
+-------------------+
1 row in set (0.00 sec)
mysql>
顯示當前庫下的所有表
show tables;
mysql> show tables;
+-------------------+
| Tables_in_company |
+-------------------+
| t_dept |
+-------------------+
1 row in set (0.00 sec)
查看表的結構
describe 表名
簡寫
desc 表名
mysql> describe t_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptno | int(11) | YES | | NULL | |
| dname | varchar(20) | YES | | NULL | |
| loc | varchar(40) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
mysql> desc t_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptno | int(11) | YES | | NULL | |
| dname | varchar(20) | YES | | NULL | |
| loc | varchar(40) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
查看表的詳細
show create table 表名
mysql> show create table t_dept;
+--------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+--------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| t_dept | CREATE TABLE `t_dept` (
`deptno` int(11) DEFAULT NULL,
`dname` varchar(20) DEFAULT NULL,
`loc` varchar(40) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+--------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
show create table t_dept \G
mysql> show create table t_dept \G
*************************** 1. row ***************************
Table: t_dept
Create Table: CREATE TABLE `t_dept` (
`deptno` int(11) DEFAULT NULL,
`dname` varchar(20) DEFAULT NULL,
`loc` varchar(40) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
刪除表
drop table 表名
drop table if exists 表名
mysql> drop table if exists t_dept;
Query OK, 0 rows affected (0.12 sec)
mysql> show tables;
Empty set (0.00 sec)
修改表名
ALTER TABLE old_table_name RENAME [TO] new_table_name
old_table_name 原表名
new_table_name 新表名
將t_dept修改為tab_dept
mysql> alter table t_dept rename tab_dept;
Query OK, 0 rows affected (0.09 sec)
mysql> show tables;
+-------------------+
| Tables_in_company |
+-------------------+
| tab_dept |
+-------------------+
1 row in set (0.00 sec)
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptno | int(11) | YES | | NULL | |
| dname | varchar(20) | YES | | NULL | |
| loc | varchar(40) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
為表增加一個字段默認在最后
ALTER TABLE table_name ADD 屬性名 屬性類型
為tab_dept增加一個字段descri varchar(20)
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptno | int(11) | YES | | NULL | |
| dname | varchar(20) | YES | | NULL | |
| loc | varchar(40) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
mysql> alter table tab_dept add descri varchar(20);
Query OK, 0 rows affected (0.33 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptno | int(11) | YES | | NULL | |
| dname | varchar(20) | YES | | NULL | |
| loc | varchar(40) | YES | | NULL | |
| descri | varchar(20) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
在表的第一個位置增加一個字段
ALTER TABLE table_name ADD 屬性名 屬性類型 first
mysql> alter table tab_dept add id int first;
Query OK, 0 rows affected (0.38 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| deptno | int(11) | YES | | NULL | |
| dname | varchar(20) | YES | | NULL | |
| loc | varchar(40) | YES | | NULL | |
| descri | varchar(20) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
在表的指定字段之后增加字段
ALTER TABLE table_name ADD 屬性名 屬性類型 AFTER 屬性名
mysql> alter table tab_dept add comm varchar(20) after dname;
Query OK, 0 rows affected (0.31 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| deptno | int(11) | YES | | NULL | |
| dname | varchar(20) | YES | | NULL | |
| comm | varchar(20) | YES | | NULL | |
| loc | varchar(40) | YES | | NULL | |
| descri | varchar(20) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
6 rows in set (0.00 sec)
刪除字段
ALTER TABLE table_name DROP 屬性名
mysql> alter table tab_dept drop comm;
Query OK, 0 rows affected (0.32 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| deptno | int(11) | YES | | NULL | |
| dname | varchar(20) | YES | | NULL | |
| loc | varchar(40) | YES | | NULL | |
| descri | varchar(20) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
字段修改-修改字段數據類型
ALTER TABLE table_name MODIFY 屬性名 數據類型
mysql> alter table tab_dept modify descri int;
Query OK, 0 rows affected (0.45 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| deptno | int(11) | YES | | NULL | |
| dname | varchar(20) | YES | | NULL | |
| loc | varchar(40) | YES | | NULL | |
| descri | int(11) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
字段修改-修改字段名稱
ALTER TABLE table_name CHANGE 舊屬性名 新屬性名 舊數據類型
mysql> alter table tab_dept change id deptid int;
Query OK, 0 rows affected (0.07 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptid | int(11) | YES | | NULL | |
| deptno | int(11) | YES | | NULL | |
| dname | varchar(20) | YES | | NULL | |
| loc | varchar(40) | YES | | NULL | |
| descri | int(11) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
字段修改-同時修改字段名稱與數據類型
ALTER TABLE table_name CHANGE 舊屬性名 新屬性名 新數據類型
mysql> alter table tab_dept change deptid id varchar(32);
Query OK, 0 rows affected (0.49 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id | varchar(32) | YES | | NULL | |
| deptno | int(11) | YES | | NULL | |
| dname | varchar(20) | YES | | NULL | |
| loc | varchar(40) | YES | | NULL | |
| descri | int(11) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
修改順序
ALTER TABLE table_name MODIFY 屬性名1 數據類型 FIRST|AFTER 屬性名2
2個屬性必須存在
將deptno調到第一個位置
mysql> alter table tab_dept modify deptno int first;
Query OK, 0 rows affected (0.33 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptno | int(11) | YES | | NULL | |
| id | varchar(32) | YES | | NULL | |
| dname | varchar(20) | YES | | NULL | |
| loc | varchar(40) | YES | | NULL | |
| descri | int(11) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
將ID放在最后
mysql> alter table tab_dept modify deptno int after descri;
Query OK, 0 rows affected (0.29 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id | varchar(32) | YES | | NULL | |
| dname | varchar(20) | YES | | NULL | |
| loc | varchar(40) | YES | | NULL | |
| descri | int(11) | YES | | NULL | |
| deptno | int(11) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
mysql> alter table tab_dept modify deptno int first;
Query OK, 0 rows affected (0.34 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table tab_dept modify id int after descri;
Query OK, 0 rows affected (0.47 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptno | int(11) | YES | | NULL | |
| dname | varchar(20) | YES | | NULL | |
| loc | varchar(40) | YES | | NULL | |
| descri | int(11) | YES | | NULL | |
| id | int(11) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
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