MySQL中的in,exists,not in,not exists查询过程对比及结论

MySQL优化之in,exists,not in,not exists的区别in与existsin查询过程结论：exists查询过程：结论：not in与not existsnot in查询过程：结论：not exists查询过程：结论： 首先我们使用两个用户表作为实例 insert into A (id,username) values (1,'张三'); insert into A (id,username) values (2,'李四'); insert into B (id,phone) values (1,'13188888888'); insert into B (id,phone