更新操作;not in 与 not exists 执行计划类似,delete 操作下持有表锁,完全不支持并发,update 操作下以 PRIMARY 索引全扫描的方式,锁住了表中数据行,阻碍了对表的 delete,update 操作,却不妨碍 insert 的并发操作,MySQL 5.6 之后的优化器对 not in 子查询做了相关优化工作,检索效率高于 not ex
DELETE 语句是用来从数据库表中删除记录的一种基础 SQL 操作。虽然 DELETE 语句很简单且直接,但在某些情况下,尤其是当我们需要根据其他表的数据进行删除时,就出现了一些问题。本文将介绍 MySQL DELETE IN 语句在使用子查询时的限制,并提供相应的解决方案和示例。 一、DELETE IN 语句的基本用法 在MySQL 中,DELETE ...
我们可以使用IN关键字来实现: DELETEFROMemployeesWHEREdepartment_idIN(1,2,3); 1. 2. 上述代码中,DELETE FROM employees表示要删除employees表中的数据,WHERE department_id IN (1, 2, 3)表示只删除department_id列的值为 1、2、3 的行。 IN关键字与OR操作符的比较 如果不使用IN关键字,我们可以使用OR操作...
mysql-py> db.city.delete().where("Name = 'Olympia'")Delete the First Record To delete the first record in the city table, use the limit() method with a value of 1. mysql-py> db.city.delete().limit(1)Delete All Records in a Table You can delete all records in a table. To...
The speed of delete operations may also be affected by factors discussed inSection 8.2.4.3, “Optimizing DELETE Statements”. To ensure that a givenDELETEstatement does not take too much time, the MySQL-specificLIMITrow_countclause forDELETEspecifies the maximum number of rows to be deleted. If...
因为子查询改为join,是可以让delete in子查询走索引;加别名呢,会走LooseScan策略,而LooseScan策略,本质上就是semi join子查询的一种执行策略。 因此,加别名就可以让delete in子查询走索引啦! 读到这里,这篇“mysql中delete in子查询不走索引问题怎么解决”文章已经介绍完毕,想要掌握这篇文章的知识点还需要大家自己...
很明显,where in 是会走索引的,但是在delete中使用不会使用索引。在网上查询了下资料,看到有人说使用inner join mysql会走索引,于是我尝试了下,使用以下sql语句: EXPLAIN DELETE phone_bak1 FROM phone_bak1 INNER JOIN phone_delete ON phone_bak1.phone = phone_delete.phone 可以看到使用inner join 确实走了...
很明显,where in 是会走索引的,但是在delete中使用不会使用索引。在网上查询了下资料,看到有人说使用inner join mysql会走索引,于是我尝试了下,使用以下sql语句: EXPLAIN DELETE phone_bak1 FROM phone_bak1 INNER JOIN phone_delete ON phone_bak1.phone = phone_delete.phone 可以看到使用inner join 确实走了...
Re: Set DELETE Limit results in error 1064 Peter Brawley December 20, 2016 12:50PM Re: Set DELETE Limit results in error 1064 Rick James December 21, 2016 12:45AM Sorry, you can't reply to this topic. It has been closed. Content reproduced on this site is the property of the respec...
which will clean chains in nat table too. Thank you! I’m having issues deleting a specific rule from my iptables. I used iptables -t nat -S to list the rule: -A POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to-source 192.168.111.111 ...