ROW_NUMBER() OVER (PARTITION BY id, name, age ORDER BY id) AS Duplicates FROM Test ) DELETE FROM CTE WHERE Duplicates > 1 GO Now check the table to make sure duplicates are being removed from table. Related:
mysqlsqlduplicatessubquerysql-delete 444 我有一个包含以下字段的表格: id (Unique) url (Unique) title company site_id 现在,我需要删除具有相同标题、公司和站点ID的行。一种方法是使用以下SQL语句以及一个脚本(PHP)来完成: SELECT title, site_id, location, id, count( * ) FROM jobs GROUP BY ...
#执行InnoDB的碎片回收mysql>altertableuserengine=InnoDB;QueryOK,0rowsaffected(9.00sec)Records:0Dupli...
分析select*fromt_table_1wheretask_idin(selectidfromt_table_2whereuid = #{uid}) 回到这条简单sql,包含子查询,按照我们的理解,mysql应该是先执行子查询:select id from t_table_2 where uid = #{uid},然后再执行外部查询:select * from t_table_1 where task_id in,但这不一定,例如我关了这个参数...
If we look at the result set, we can easily understand thatBookNumber: 3andBookNumber: 4are duplicate rows. Previously, it was explained in detailhow to remove duplicates in SQL. We must delete them to keep the database consistent.
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delete对SQL的影响 未删除前的SQL执行情况 #插入100W数据 mysql> call insert_user_data(1000000); Query OK,0rows affected (35.99sec) #添加相关索引 mysql> alter table user add index idx_name(name), add index idx_phone(phone); Query OK,0rows affected (6.00sec) Records:0Duplicates:0Warnings:0...
/* Set no locks when applying log in online table rebuild. */ } else if (allow_duplicates) { /* If the SQL-query will update or replace duplicate key we will take X-lock for duplicates ( REPLACE, LOAD DATAFILE REPLACE, INSERT ON DUPLICATE KEY UPDATE). */ ...
开始我们拿sql到数据库查询平台查库执行计划,无奈这个平台有bug,delete语句无法查看,所以我们改成select,“应该”是一样。这个“应该”加了双引号,导致我们走了一点弯路。 EXPLAIN SELECT * from t_table_1 where task_id in (select id from t_table_2 where uid = 1) ...
> create table test_del select *from t_fund_info; Query OK, 1998067 rows affected (33.82 sec) Records: 1998067 Duplicates: 0 Warnings: 0这个时候我们来看看存在大量数据的情况下,修改存储引擎的情况。 可以看到操作的时间还是有着天壤之别 > alter table test_del engine=innodb; ...