这两个查询之间有区别吗? [英] Is there a difference between these two queries?

问题描述

我认为这是一个非常简单的问题，但我找不到令人满意的答案. 这两个查询之间有区别吗?

Well, pretty simple question I think, but I can't find a satisfying answer. Is there a difference between these two queries?

SELECT * FROM table WHERE column1 = 'x' OR column2 = 'x'

SELECT * FROM table WHERE (column1 = 'x' OR column2 = 'x')

预先感谢

推荐答案

现在，您的查询中存在否差异.

Right now there is NO difference in your queries.

如果在查询中添加AND条件，则会有所不同.

There would be difference if there would be AND condition as addition in your query.

例如

SELECT * FROM table WHERE id=1 AND column1 = 'x' OR column2 = 'x'

和

SELECT * FROM table WHERE id=1 AND (column1 = 'x' OR column2 = 'x')

注意

SELECT * FROM table WHERE id=1 AND column1 = 'x' OR column2 = 'x'

将等同于

SELECT * FROM table WHERE (id=1 AND column1 = 'x') OR column2 = 'x'

这篇关于这两个查询之间有区别吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！