sql优化之小表驱动大表
时间: 2023-08-27 08:21:10 浏览: 53
在优化SQL中,小表驱动大表是一种常见的优化策略。它的基本思想是,将小表作为驱动表,大表作为被驱动表,以减少循环的次数,提高查询效率。
在引用中的例子中,通过使用left join将user表与class表进行连接查询。如果将user表作为驱动表,则需要循环10000次才能查询出结果。而如果将class表作为驱动表,则只需要循环20次就可以查询出结果。这是因为驱动表的记录数较少,循环次数更少,查<span class="em">1</span><span class="em">2</span><span class="em">3</span>
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