SQL 查找违反 UNIQUE together 索引的行 [英] SQL Find rows that violate UNIQUE together index

问题描述

我想在表中的两个(或更多)列上放置唯一索引，但我得到发现重复键".如何选择那些导致重复的行?

i want to put unique index on two (or more) columns in a table, but i get "duplicate keys found". How to select those rows which cause duplication?

推荐答案

您可以使用 Group By 和 Having 来解决这个问题:

You can use Group By and Having for this:

SELECT col1,
       col2
FROM   table
GROUP  BY col1,
          col2
HAVING Count(*) > 1

基本上 - 将值分组，然后过滤多个实例.

Basically - group the values, then filter for instances where there is more than one.

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