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Home Backend Development PHP Tutorial Mysql 如何插入和自增id相同的值?

Mysql 如何插入和自增id相同的值?

Jun 06, 2016 pm 08:23 PM
mysql php

假设数据库test表有3个字段

1

2

3

<code>id(自增)

name

order</code>

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现在要插入一条数据 让order 和 id 的值相等
我是 先插入一条数据
再获取到插入的id
然后 update 将order设成id值
有没有办法插入的时候就让id 和order相等

还是先 select max(id) from test
再执行插入?

这种情况一定要两条语句才能搞定吗?

回复内容:

假设数据库test表有3个字段

1

2

3

<code>id(自增)

name

order</code>

Copy after login
Copy after login

现在要插入一条数据 让order 和 id 的值相等
我是 先插入一条数据
再获取到插入的id
然后 update 将order设成id值
有没有办法插入的时候就让id 和order相等

还是先 select max(id) from test
再执行插入?

这种情况一定要两条语句才能搞定吗?

你的这个设计不合理,看得出来你这个order是用来作为排序字段的,并且希望有人工调整的余地,而不是简单的设计成按照主键排序,那这样的话你在select的时候直接用order by `order`, `id` 就解决了这个问题,这样的话order字段只要有一个默认值就可以了,例如10000,优先用此字段排序,然后用id排序

当然还有记得加索引


题外话,不要用mysql的关键字作为字段名,也就是order这类的名字,建议改成priority之类的名字!

可以用Mysql的触发器实现

也可以用事务去处理

获取最后一条插入的id的话,SET @lastid = LAST_INSERT_ID(); 是不是要比select max(id) from test要好?

想了一个很猥琐的办法就是把 order 也设置自增。

一个值为什么要用两个字段?

楼上许多答案有考虑不周全的地方。

一个表无法设置两个自增字段的。

无法在insert的过程中获得当前生成的id, 只能通过两条语句去做吧。 两次操作有什么问题吗?

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