090-where后面的行子查询

#查询员工编号最小并且工资最高的员工信息
#此员工不一定存在

以前的做法

SELECT *
FROM employees
WHERE employee_id=(
	SELECT MIN(employee_id)
	FROM employees
)AND salary=(
	SELECT MAX(salary)
	FROM employees
);

行子查询代替：筛选条件都为等于时可以使用

SELECT *
FROM employees
WHERE (employee_id,salary)=(
	SELECT MIN(employee_id),MAX(salary)
	FROM employees
)