MySQL 添加序号列

alter table abc add num int unsigned auto_increment

如果同时为主键的话,可以这样写

alter table abc add num int unsigned primary key auto_increment

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to:数据库强者 不ok

alter table abc change num num int primary key auto_increment

前提是你的表中不能存在主键,否则请使用:

alter table abc change num num int auto_increment

一般情况下增长都是主键

mysql>

select

*

from

a

+-----+

|

col

|

+-----+

|

0

|

|

1

|

|

2

|

|

3

|

|

4

|

|

5

|

|

6

|

|

7

|

+-----+

8

rows

in

set

(0.00

sec)

mysql>

set

@i

:=

0

select

@i

:=

@i

+

1

as

`order`,

a.*

from

a

order

by

col

desc

+-------+-----+

|

order

|

col

|

+-------+-----+

|

1

|

7

|

|

2

|

6

|

|

3

|

5

|

|

4

|

4

|

|

5

|

3

|

|

6

|

2

|

|

7

|

1

|

|

8

|

0

|

+-------+-----+

8

rows

in

set

(0.00

sec)

mysql>

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