语法
Exists(完整的查询语句)
结果:1 or 0
exists查询:先执行外查询 或 子查询,某一个字段的值 再根据结果过滤
子查询 涉及到了 主查询的字段
案例
#查询有员工的部门名 SELECT department_name FROM departments d WHERE EXISTS( SELECT * FROM employees e WHERE d.'department_id' = e.'department_id' );
#IN的方式 SELECT department_name FROM departments d WHERE d.'department_id' IN( SELECT department_id FROM employees )
标签:exists,查询,MySQL,department,WHERE,id,SELECT From: https://www.cnblogs.com/yzhone/p/16863244.html