超级会员免费看
本文详细介绍了MySQL 8.0如何使用半连接策略优化IN和EXISTS子查询，以提高查询效率。通过避免不必要的数据重复和利用如表提取、重复消除、首次匹配和宽松扫描等策略，实现更高效的子查询执行。从MySQL 8.0.17开始，某些子查询的否定形式也会被转换为反连接操作，进一步提升性能。
8.2.2.1 Optimizing IN and EXISTS Subquery Predicates with Semijoin Transformations
A semijoin is a preparation-time transformation that enables multiple execution strategies such as table pullout, duplicate weedout, first match, loose scan, and materialization. The optimizer uses semijoin strategies to improve subquery execution, as described in this section.
For an inner joi
订阅专栏 解锁全文
扫一扫
被折叠的 条评论
为什么被折叠?
到【灌水乐园】发言
