mysql - 如何将两个 COUNT() 语句合二为一并求出差值？

Question

我怎样才能将以下两个查询合并为一个以得到 result 作为两个计数的差值。或者结果是:

result = vote1 - vote2

SELECT COUNT(id) AS vote1 FROM votes WHERE votes.voteTypeId = @voteType1 AND votes.userId = @userId
SELECT COUNT(id) AS vote2 FROM votes WHERE votes.voteTypeId = @voteType2 AND votes.userId = @userId

Answer 1

SELECT  SUM(votetypeid = @votetype1) - SUM(votetypeid = @votetype2)
FROM    votes
WHERE   userid = @userid
        AND votetypeid IN (@votetype1, @votetype2)