SQL内部联接返回的行比预期多 [英] SQL Inner Join Returns WAY More Rows Than Expected

问题描述

当每个表只有340行时，以下查询将返回> 7000行.

The following query returns >7000 rows when each table only has 340 rows.

SELECT Config.Spec, TempTable.Spec FROM Confg INNER JOIN TempTable on Config.Spec = TempTable.Spec

为什么会这样?如果INNER JOIN仅在两个表中都有匹配项时才返回一行，那为什么还要为匹配项返回多行呢?

Why would this happen? If an INNER JOIN only returns a row if there is a match in both tables then why would it return multiple rows for a match.

推荐答案

如果TempTable中的Spec值与Confg中的Spec值相同，则存在多个行得到重复的行，反之亦然.

If there is more than one row with the same Spec value in TempTable for the same Spec value in Confg, then you will get duplicate rows, and vice versa.

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