SQL中的UNION之后的WHERE语句? [英] WHERE statement after a UNION in SQL?

问题描述

在SQL/MySQL中，如何在UNION之后应用WHERE语句?

How do I apply a WHERE statement after a UNION in SQL/MySQL?

推荐答案

如果要将WHERE子句应用于UNION的结果，则必须将UNION嵌入到FROM子句中:

If you want to apply the WHERE clause to the result of the UNION, then you have to embed the UNION in the FROM clause:

SELECT *
  FROM (SELECT * FROM TableA
        UNION
        SELECT * FROM TableB
       ) AS U
 WHERE U.Col1 = ...

我假设TableA和TableB是联合兼容的.当然，您也可以将WHERE子句应用于UNION中的每个单独的SELECT语句.

I'm assuming TableA and TableB are union-compatible. You could also apply a WHERE clause to each of the individual SELECT statements in the UNION, of course.

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