[打卡]万物不及桐神 2024/5.14

-- 单行子查询

-- 单行子查询操作符：= != <> > >= <=

-- 习题 查询工资大于149号员工工资的员工信息
SELECT employee_id,salary
FROM employees
WHERE salary>(
SELECT salary
FROM employees
WHERE employee_id=149
);

-- 习题：返回job_id 与141号员工相同，salary 比143员工工资多的员工姓名，job_id和工资
SELECT last_name,job_id,salary
FROM employees
WHERE job_id=(
SELECT job_id
FROM employees
WHERE employee_id=141
)
AND salary>(
SELECT salary
FROM employees
WHERE employee_id=143);

/* 子查询编写技巧
1.从里往外写
2.从外往里写
*/
-- 中英互换
-- 习题：返回公司工资最少的员工last_name，job_id和salary

SELECT last_name,job_id,salary
FROM employees
WHERE salary=(
SELECT MIN(salary)
FROM employees
)


-- 查询与141号员工的manager—id和department_id相同的employee——id，manager_id，department—id
SELECT employee_id,manager_id,department_id
FROM employees
WHERE manager_id=(
SELECT manager_id
FROM employees
WHERE employee_id=141
)
AND department_id=(
SELECT department_id
FROM employees
WHERE employee_id=141
)
AND employee_id<>141;
-- 不等于141 （上面）

-- 方式二
SELECT employee_id,manager_id,department_id
FROM employees
WHERE (manager_id,department_id)=(
SELECT manager_id,department_id
FROM employees
WHERE employee_id=141
)
AND employee_id !=141;

-- 习题：查询最低工资大于110号最低工资的部门id和其最低工资
SELECT department_id,salary
FROM employees
WHERE department_id IS NOT NULL
GROUP BY department_id
HAVING MIN(salary)>(
SELECT MIN(salary)
FROM employees
WHERE department_id=60
);

-- 非法使用子查询
-- 等于后面必须是一个准确的数
SELECT employee_id,last_name
FROM employees
WHERE salary=(
SELECT MIN(salary)
FROM employees
GROUP BY department_id
)；