如何比较两个查询结果在MySQL中的相等? [英] How to compare two query results for equality in MySQL?
问题描述
我是MySQL用户。我有两个查询,我希望比较它们的结果是否相等。我想用单个查询返回true或false这样做,所以我的两个查询很可能采取子查询的形式。
I'm a MySQL user. I have two queries, and I wish to compare their results for equality. I would like to do this with a single query which would return true or false, so each of my two queries would most likely take the form of sub-queries.
I希望避免从两个查询返回结果并在应用程序级别进行比较,以减少通信和提高性能。我也希望避免在数据库级别循环结果,如果可能,但如果没有其他方式,那么。
I would like to avoid returning the results from both queries and comparing them at the application level, to cut down on communication and to improve performance. I would also like to avoid looping over the results at the database level if possile, but if there's no other way, so be it.
我已经搜索高和低一个例子,如何做到这一点,但是空手而来。有些示例代码会非常感谢,因为我是SQL编程的新手。非常感谢!
I have searched high and low for an example on how to do this, but have come up empty handed. Some sample code would be most appreciated, because I'm a newbie to SQL programming. Thanks!
注意:我正在寻找一个可以处理任意两个任意查询的解决方案,发布我的两个查询碰巧是。
Note: I'm looking for a solution which would work with any two arbitrary queries, so I'm going to refrain from posting what my two queries happen to be.
推荐答案
SELECT
CASE WHEN count1 = count2 AND count1 = count3 THEN 'identical' ELSE 'mis-matched' END
FROM
(
SELECT
(SELECT COUNT(*) FROM <query1>) AS count1,
(SELECT COUNT(*) FROM <query2>) AS count2,
(SELECT COUNT(*) FROM (SELECT * FROM query1 UNION SELECT * FROM query2) AS unioned) AS count3
)
AS counts
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