数据库小技巧：使用distinct去除重复行

这里有2个表

问题question表

楼层question_floor表

 

 

需求：已知某用户的id为uid，实现“我的回复”功能，即查看我回复的所有问题

遇到的问题：如果直接对question表和question_floor表进行连接查询的话，即

SELECT question.qid qid, question.uid uid, " +
        "question.ask_time, question.title, question.content, " +
        "question.current_floor, question.credit, question.is_resolved " +
        "FROM question, question_floor " +
        "WHERE question_floor.uid = #{uid} " +
        "AND question_floor.fid != 1 ORDER BY question.ask_time desc

当A多次回复帖子P时，A点击"我的回复"按钮，将会显示多条帖子P的记录。

解决方案：使用distinct

SELECT DISTINCT question.qid qid, question.uid uid, " +
        "question.ask_time, question.title, question.content, " +
        "question.current_floor, question.credit, question.is_resolved " +
        "FROM question, question_floor " +
        "WHERE question_floor.uid = #{uid} " +
        "AND question_floor.fid != 1 ORDER BY question.ask_time desc