修改表的结构操作，有下面几种。1、修改列名
2、修改表的名字
3、修改列的类型
4、增加某列
5、删除某列相似的语法：alter table TableName xxx(操作)
一、修改列名
①、语法：
ALTER TABLE TABLENAME CHANGE 原列名 想改成的列名 列类型;
②、示例：
1、查看原表的结构
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> desc MyTable;
+---------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| stuname | varchar(10) | YES | | NULL | |
+---------+-------------+------+-----+---------+-------+
1 row in set (0.01 sec)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2、修改某一列想改的列名
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> alter table MyTable change stuname sname varchar(10);
Query OK, 0 rows affected (0.02 sec)
Records: 0 Duplicates: 0 Warnings: 0
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3、查看结果
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> desc MyTable;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| sname | varchar(10) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
1 row in set (0.01 sec)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
二、修改表的名字
①、基本语法：
修改表的名字的方法有两种：
1、ALTER TABLE TABLENAME RENAME NEWTABLENAME;
2、RENAME TABLE TABLENAME TO NEWTABLENAME;
②、示例
1、查看表的原名字,假如我们要更改FirTable_COPY 为 FCS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| FirTable |
| FirTable_COPY |
| FirTable_COPY2 |
| FirstTable |
| MT |
+----------------+
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2、运用第一种方法修改
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> alter table FirTable_COPY rename FC;
Query OK, 0 rows affected (2.22 sec)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3、查看结果
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| FC |
| FirTable |
| FirTable_COPY2 |
| FirstTable |
| MT |
+----------------+
5 rows in set (0.00 sec)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4、发现手残打错了，运用第二种方法修改(当然也可以进行用第一种办法)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> rename table FC to FCS;
Query OK, 0 rows affected (0.04 sec)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
5、查看结果
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| FCS |
| FirTable |
| FirTable_COPY2 |
| FirstTable |
| MT |
+----------------+
5 rows in set (0.00 sec)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
三、修改列的类型
①、基本语法：
ALTER TABLE TABLENAME MODIFY 列名 想改的类型
②、示例：
1、查看原表格的结构，假如要改变sno的int变成varchar(13)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> desc FCS;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| sno | int(11) | YES | | NULL | |
| sname | varchar(10) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.01 sec)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2、修改语句
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> ALTER TABLE FCS MODIFY sno varchar(13);
Query OK, 0 rows affected (0.15 sec)
Records: 0 Duplicates: 0 Warnings: 0
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3、查看结果
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> desc FCS;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| sno | varchar(13) | YES | | NULL | |
| sname | varchar(10) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.03 sec)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
四、增加列
①、语法：
ALTER TABLE TABLENAME ADD 列名 类型;
②、示例：
1、原来表的结构是如下情况：
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> desc MyTable;
+---------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| stuname | varchar(10) | YES | | NULL | |
+---------+-------------+------+-----+---------+-------+
1 row in set (0.01 sec)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2、进行增加操作
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> alter table MyTable add stuNum long;
Query OK, 0 rows affected (0.15 sec)
Records: 0 Duplicates: 0 Warnings: 0
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3、完成之后的操作
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> desc MyTable;
+---------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| stuname | varchar(10) | YES | | NULL | |
| stuNum | mediumtext | YES | | NULL | |
+---------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
③、常见错误：
1、添加了相同名字的列
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> alter table MyTable add stuNum long;
ERROR 1060 (42S21): Duplicate column name 'stuNum'
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2、同时添加了很多个列
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> alter table MyTable add stuName varchar(10), stuCount varchar(16);
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'stuCount varchar(16)' at line 1
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3、修改没有权限操作的库的表
这里以information_schema为例
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> alter table INNODB_FT_CONFIG add count int;
ERROR 1044 (42000): Access denied for user 'root'@'localhost' to database 'information_schema'
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
五、删除某列
①、语法：ALTER TABLE TABLENAME DROP 列名
②、示例：
1、MyTable的原始状态
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> desc MyTable;
+---------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| stuname | varchar(10) | YES | | NULL | |
| stuNum | mediumtext | YES | | NULL | |
+---------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2、删除的语句
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> ALTER TABLE MyTable DROP stuNum;
Query OK, 0 rows affected (0.15 sec)
Records: 0 Duplicates: 0 Warnings: 0
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3、操作后MyTable的结构
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mysql> desc MyTable;
+---------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| stuname | varchar(10) | YES | | NULL | |
+---------+-------------+------+-----+---------+-------+
1 row in set (0.01 sec)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~