Mysql一些復(fù)雜的sql語(yǔ)句(查詢與刪除重復(fù)的行)
發(fā)表時(shí)間：2023-08-28 來(lái)源：明輝站整理相關(guān)軟件相關(guān)文章人氣：
[摘要]這篇文章主要介紹了Mysql一些復(fù)雜的sql語(yǔ)句(查詢與刪除重復(fù)的行),需要的朋友可以參考下1.查找重復(fù)的行SELECT * FROM blog_user_relation a WHERE (a.account_instance_id,a.follow_account_instance_id) I...
這篇文章主要介紹了Mysql一些復(fù)雜的sql語(yǔ)句(查詢與刪除重復(fù)的行),需要的朋友可以參考下
1.查找重復(fù)的行
SELECT * FROM blog_user_relation a WHERE (a.account_instance_id,a.follow_account_instance_id)
IN (SELECT account_instance_id,follow_account_instance_id FROM blog_user_relation GROUP BY account_instance_id, follow_account_instance_id HAVING
COUNT(*) > 1)
2.刪除重復(fù)的行(保留一條)
PS：因?yàn)閙ysql的delete，如果被刪的表的where條件里有in，且in里面也有此表，那就刪除不了。
/*創(chuàng)建個(gè)臨時(shí)表*/
CREATE TABLE blog_user_relation_temp AS
(
SELECT * FROM blog_user_relation a WHERE
(a.account_instance_id,a.follow_account_instance_id)
IN ( SELECT account_instance_id,follow_account_instance_id FROM blog_user_relation GROUP BY account_instance_id, follow_account_instance_id HAVING COUNT(*) > 1)
AND
relation_id
NOT IN (SELECT MIN(relation_id) FROM blog_user_relation GROUP BY account_instance_id, follow_account_instance_id HAVING COUNT(*)>1));
/*刪除數(shù)據(jù)*/
DELETE FROM `blog_user_relation` WHERE relation_id IN (SELECT relation_id FROM blog_user_relation_temp);
/*刪除臨時(shí)表*/
DROP TABLE blog_user_relation_temp;
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