MySQL-sql99-子查询-列子查询、行子查询

列子查询（多行子查询）

案例：返回location_id是1400或1700的部门中所有员工姓名

# ①查询location_id是1400或1700的部门编号
SELECT `department_id`
FROM `departments`
WHERE `location_id` IN(1400,1700);

是1列多行

满足列子查询

# ②查询员工姓名，要求部门号是①列表中的某一个
SELECT `last_name`
FROM `employees`
WHERE `department_id` IN (
	SELECT `department_id`
	FROM `departments`
	WHERE `location_id` IN(1400,1700)
);

案例：返回其他工种中比job_id为'IT_PROG'工种任一工资低的员工的员工号、姓名、job_id以及salary

# ①查询job_id为'IT_PROG'部门任一工资
SELECT DISTINCT `salary`
FROM `employees`
WHERE `job_id`='IT_PROG';

# ②查询员工号、姓名、job_id以及salary salary<any(①)
SELECT `last_name`,`employee_id`,`job_id`,`salary`
FROM `employees`
WHERE `salary`<ANY(
	SELECT DISTINCT `salary`
	FROM `employees`
	WHERE `job_id`='IT_PROG')
AND job_id<>'IT_PROG';

也可以用max()来代替any()

# ①查询job_id为'IT_PROG'部门任一工资
SELECT DISTINCT `salary`
FROM `employees`
WHERE `job_id`='IT_PROG';

# ②查询员工号、姓名、job_id以及salary salary<any(①)
SELECT `last_name`,`employee_id`,`job_id`,`salary`
FROM `employees`
WHERE `salary`<(
	SELECT MAX(`salary`)
	FROM `employees`
	WHERE `job_id`='IT_PROG')
AND job_id<>'IT_PROG';

结果还是一样的

返回其它部门中比job_id为'IT_PROG'部门所有工资部低的员工的员工号、姓名、job_id 以及salary

#返回其它部门中比job_id为'IT_PROG'部门所有工资部低的员工的员工号、姓名、job_id 以及salary
#① 先查询job_id为'IT_PROG'部门的所有工资
SELECT DISTINCT `salary`
FROM `employees`
WHERE `job_id`='IT_PROG';

#② 查询员工的员工号、姓名、job_id 以及salary，并且工资比①中都低
SELECT `employee_id`,`last_name`,`job_id`,`salary`
FROM `employees`
WHERE salary <ALL(
	SELECT DISTINCT `salary`
	FROM `employees`
	WHERE `job_id`='IT_PROG'
) AND `job_id`<>'IT_PROG';

或者换成min(salary)

#① 先查询job_id为'IT_PROG'部门的所有工资
SELECT DISTINCT `salary`
FROM `employees`
WHERE `job_id`='IT_PROG';

#② 查询员工的员工号、姓名、job_id 以及salary，并且工资比①中都低
SELECT `employee_id`,`last_name`,`job_id`,`salary`
FROM `employees`
WHERE salary <(
	SELECT MIN(`salary`)
	FROM `employees`
	WHERE `job_id`='IT_PROG'
) AND `job_id`<>'IT_PROG';

同样的效果

其中第一个案例

案例：返回location_id是1400或1700的部门中所有员工姓名

# 案例：返回location_id是1400或1700的部门中所有员工姓名
SELECT `last_name`
FROM `employees`
WHERE `department_id` in (
	SELECT `department_id`
	FROM `departments`
	WHERE `location_id` IN(1400,1700)
);

代码是上面的 也可以用any代替in

# 案例：返回location_id是1400或1700的部门中所有员工姓名
SELECT `last_name`
FROM `employees`
WHERE `department_id` =ANY (
	SELECT `department_id`
	FROM `departments`
	WHERE `location_id` IN(1400,1700)
);

效果是一样的

行子查询(结果集一行多列或多行多列)

引入

案例:查询员工编号最小并且工资最高的员工信息

#①查询最小的员工编号
SELECT MIN(`employee_id`)
FROM `employees`;

#查询最高工资
SELECT MAX(`salary`)
FROM `employees`;

#查询员工信息
SELECT *
FROM `employees`
WHERE `employee_id`=(
	SELECT MIN(`employee_id`)
	FROM `employees`
)
AND `salary`=(
	SELECT MAX(`salary`)
	FROM `employees`
)

行子查询是有条件的 当筛选条件全部都是等于的情况时候 用行子查询

select *
from `employees`
where (`employee_id`,`salary`)=
(
select min(`employee_id`),max(`salary`)
from `employees`
);