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Mysql中查詢與刪除重復(fù)行的一些復(fù)雜的sql語句

[摘要]這篇文章主要介紹了Mysql一些復(fù)雜的sql語句(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語句(查詢刪除重復(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:因為mysql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)建個臨時表*/
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);

/*刪除臨時表*/
DROP TABLE blog_user_relation_temp;

以上就是Mysql中查詢與刪除重復(fù)行的一些復(fù)雜的sql語句的詳細內(nèi)容,更多請關(guān)注php中文網(wǎng)其它相關(guān)文章!


學(xué)習(xí)教程快速掌握從入門到精通的SQL知識。