mysql alter table修改表命令整理

Posted 2023-03-09

参考技术A mysql
ALTER
TABLE命令用于修改表结构，例如添加/修改/删除字段、索引、主键等等，本文章通过实例向大家介绍MYSQL
ALTER
TABLE语句的使用方法，
MySQL
ALTER语法如下：
ALTER
[IGNORE]
TABLE
tbl_name
alter_spec
[,
alter_spec
...]
alter_specification:
ADD
[COLUMN]
create_definition
[FIRST
|
AFTER
column_name
]
or
ADD
INDEX
[index_name]
(index_col_name,...)
or
ADD
PRIMARY
KEY
(index_col_name,...)
or
ADD
UNIQUE
[index_name]
(index_col_name,...)
or
ALTER
[COLUMN]
col_name
SET
DEFAULT
literal
|
DROP
DEFAULT
or
CHANGE
[COLUMN]
old_col_name
create_definition
or
MODIFY
[COLUMN]
create_definition
or
DROP
[COLUMN]
col_name
or
DROP
PRIMARY
KEY
or
DROP
INDEX
index_name
or
RENAME
[AS]
new_tbl_name
or
table_options
下面来看几个实例：
1、向表employee中添加Account_Number字段并设置其字段类型为INT
ALTER
TABLE
employee
ADD
COLUMN
Account_Number
INT
2、修改表employee中的ID字段为索引
ALTER
TABLE
employee
ADD
INDEX
(ID)
3、修改表employee中的ID字段为主键PRIMARY
KEY
ALTER
TABLE
employee
ADD
PRIMARY
KEY
(ID)
4、修改表employee中的ID字段为唯一索引UNIQUE
ALTER
TABLE
employee
ADD
UNIQUE
(ID)
5、将employee表中的id字段重命名为salary并设置其数据类型为int
ALTER
TABLE
employee
CHANGE
ID
salary
INT
6、删除employee表中的Customer_ID字段
ALTER
TABLE
employee
DROP
Customer_ID
7、删除employee表中所有主键
ALTER
TABLE
employee
DROP
PRIMARY
KEY
8、删除employee表中字段Customer_ID的索引，只是将Customer_ID的索引取消，不会删除Customer_ID字段。
ALTER
TABLE
employee
DROP
INDEX
Customer_ID
9、修改employee表中First_Name的字段类型为varchar(100)
ALTER
TABLE
employee
MODIFY
First_Name
varchar(100)
10、将表employee重命名为Customer
ALTER
TABLE
employee
RENAME
Customer
11、多命令写在一起：
mysql>
ALTER
TABLE
Books
->
ADD
PRIMARY
KEY
(BookID),
->
ADD
CONSTRAINT
fk_1
FOREIGN
KEY
(PubID)
REFERENCES
Publishers
(PubID),
->
ADD
COLUMN
Format
ENUM('paperback',
'hardcover')
NOT
NULL
AFTER
BookName;
感谢阅读此文，希望能帮助到大家，谢谢大家对本站的支持！