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一、需求
用户答题，共3道，必须3题都答完才能提交。
目的：要查询用户答对了几题，答错了几题。（当然此处可以只查答对的题目数，用3减即得答错题的题目数）
二、sql
select * from (select count(1) rightCount from (select * from (select * from mic_td_exercise_push_problem mp where mp.push_id = 347 order by mp.create_time desc) where rownum <= 3) t1 where t1.is_correct = 1), (select count(1) wrongCount from (select * from (select * from mic_td_exercise_push_problem mp where mp.push_id = 347 order by mp.create_time desc) where rownum <= 3) t1 where t1.is_correct = 2)
将两个查询结果进行联合查询，就得到了一条记录，两个向要的结果。
oracle将两个结果连接后进行查询，得到两个查询的联合结果
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原文地址：http://www.cnblogs.com/brolanda/p/4523854.html
