mysql alter table修改表命令整理

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！

try

{

$dbh

=

new

PDO('mysql:host=localhostdbname=test',

$user,

$pass)

foreach($dbh->query('SELECT

*

from

FOO')

as

$row)

{

print_r($row)

}

$dbh

=

null//释放资源

}

catch

(PDOException

$e)

{

print

"错误!:

"

.

$e->getMessage()

.

"<br></br>"

die()

}

//执行删除 *** 作，插入、修改与此类似，更改SQL语句即可

$count

=

$dbh->exec("DELETE

FROM

fruit

WHERE

colour

=

'red'")