MySQL 更改表添加主键语法错误的列 [英] MySQL alter table add column with primary key syntax error

问题描述

我正在尝试向我的数据库表之一添加一列，但出现语法错误我似乎找不到问题...

I'm trying to add a column to one of of my database tables, but there is a syntax error and I can't seem to find the problem...

我当前的数据库表如下所示:

My current database table looks like this:

component   +  tag_id  +  item_id
------------|----------|-----------
com_content |    23    |    2642
com_content |    26    |    3481
com_content |    35    |    1868
com_content |    85    |    5827
com_content |    89    |    7882

我希望它看起来像这样，其中id"是自动递增的，所有列都是主键的一部分

I want it to look like this, where 'id' is auto increment and all columns part of the primary key

 id  +  component   +  tag_id  +  item_id
-----|--------------|----------|-----------
  1  |  com_content |    23    |    2642
  2  |  com_content |    26    |    3481
  3  |  com_content |    35    |    1868
  4  |  com_content |    85    |    5827
  5  |  com_content |    89    |    7882

这是我的查询:

DROP PRIMARY KEY
ALTER TABLE gitags_items
ADD COLUMN id INT NOT NULL AUTO_INCREMENT FIRST
PRIMARY KEY (id,component,tag_id,item_id)

但是我收到此错误消息:

However I'm getting this error message:

#1064 - 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 'PRIMARY KEY ALTER TABLE gitags_items ADD COLUMN id INT NOT NULL AUTO_INC' at line 1

任何帮助/指针将不胜感激

Any help/pointers would be much appreciated

推荐答案

'ALTER TABLE' 位必须先出现，然后每个部分必须用逗号分隔:

The 'ALTER TABLE' bit must come first, and then each part must be seperated by a comma:

ALTER TABLE gitags_items
DROP PRIMARY KEY,
ADD COLUMN id INT NOT NULL AUTO_INCREMENT FIRST,
ADD PRIMARY KEY (id,component,tag_id,item_id);

但我不确定您是否可以在同一个状态中删除和创建主键.

but I'm not sure if you can drop and create a primary key in the same staatement.

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