题目:查找员工表中薪资倒数第二的员工信息
答案:SELECT *
FROM employees m
WHERE 2 = (SELECT COUNT(DISTINCT salary )
FROM employees
WHERE salary <= m.salary);
不明白之处:主查询中的筛选条件——(select count(distinct salary) from employees where salary<=m.salary)=2 中等号左侧返回的结果是一个数值,不符合where子句的语法——where 字段名称 操作符 值
求教大神指点,感激不尽!