mysql联查中使用if和group by会让你的结果不是你想要的

Posted 2021-01-25 ALU的编程技术博客

mysql中的if语句遇到统计count group by的时候会出现不准确的情况，原因是分组后if条件的结果以第一条为准，不会跟着分组

 

例如：

SELECT SQL_NO_CACHE t1.*,t2.nick_name,t2.avatar,IF(t1.user_id=104080,1,0) AS is_owner,
IF(t4.user_id=104080,t4.vote_val,‘N‘) AS is_voted,
COUNT(DISTINCT t5.user_id) AS voted_up_count,
COUNT(DISTINCT tt.user_id) AS voted_down_count,
COUNT(DISTINCT t6.id) AS comment_count,
IF(t7.user_id=104080,1,0) AS is_collected 
FROM answer t1 
JOIN user t2 ON t1.user_id = t2.id 
LEFT JOIN answer_vote t4 ON t4.item_id = t1.id 
LEFT JOIN answer_vote t5 ON t5.item_id = t1.id AND t5.vote_val = ‘U‘ 
LEFT JOIN answer_vote tt ON tt.item_id = t1.id AND tt.vote_val = ‘D‘ 
LEFT JOIN answer_comment t6 ON t6.item_id = t1.id 
LEFT JOIN answer_collection t7 ON t7.item_id = t1.id 
GROUP BY id HAVING approved = 1 AND question_id = 100131
ORDER BY voted_up_count desc,id desc LIMIT 10 OFFSET 0;

 

未完待续......