Mysql数据库中的子查询、标量子查询、行子查询、列子查询及表子查询实例代码

SELECT 字段列表
FROM 表名
WHERE 字段 运算符 (
    SELECT 字段
    FROM 表名
    WHERE 条件
);

SELECT emp.*
FROM emp
WHERE emp.dept_id = (
    SELECT dept.id
    FROM dept
    WHERE dept.name = '研发部'
);

SELECT name, salary
FROM employees
WHERE salary > (
    SELECT AVG(salary)
    FROM employees
);

SELECT name
FROM employees
WHERE dept_id IN (
    SELECT id
    FROM departments
    WHERE location = '上海'
);

SELECT name
FROM employees
WHERE salary > ANY (
    SELECT salary FROM employees WHERE dept_id = 3
);

SELECT name
FROM employees
WHERE salary > ALL (
    SELECT salary FROM employees WHERE dept_id = 3
);

-- 查询销售部和市场部的所有员工的信息
select id from dept where name='销售部' or name='市场部';  -- 返回值（2，4）
select * from emp33 where id in(2,4)
等价于
select* from emp33 where id in (select id from dept where name='销售部' or name='市场部');

SELECT emp.*
FROM emp
WHERE (emp.dept_id, emp.job) = (
    SELECT emp.dept_id, emp.job
    FROM emp
    WHERE emp.name = '张三'
);

SELECT name
FROM employees
WHERE (salary, job_id) = (
    SELECT salary, job_id
    FROM employees
    WHERE name = '张三'
);

select * from emp33 where (salary,managerid) =(select salary,managerid from emp33 where name='张无忌');

select * from emp33 where managerid=(select managerid from emp33 where name='张无忌') and salary=(select salary from emp33 where name='张无忌');

SELECT temp.dept_id, temp.avg_sal
FROM (
    SELECT emp.dept_id, AVG(emp.salary) AS avg_sal
    FROM emp
    GROUP BY emp.dept_id
) AS temp;

SELECT emp.name
FROM emp
WHERE emp.dept_id = (
    SELECT dept.id
    FROM dept
    WHERE dept.name = '财务部'
);

SELECT temp.name
FROM (
    SELECT emp.name
    FROM emp
    WHERE emp.salary > 10000
) AS temp;

SELECT
    emp.name,
    (
        SELECT dept.name
        FROM dept
        WHERE dept.id = emp.dept_id
    ) AS dept_name
FROM emp;

SELECT emp.*
FROM emp
WHERE emp.dept_id IN (
    SELECT dept.id
    FROM dept
);

SELECT emp.*
FROM emp
WHERE emp.salary > ANY (
    SELECT emp.salary
    FROM emp
    WHERE emp.dept_id = 1
);

SELECT emp.*
FROM emp
WHERE emp.salary > ALL (
    SELECT emp.salary
    FROM emp
    WHERE emp.dept_id = 2
);

SELECT emp.*
FROM emp
WHERE EXISTS (
    SELECT *
    FROM dept
    WHERE dept.id = emp.dept_id
);

-- 子查询写法
SELECT emp.name
FROM emp
WHERE emp.dept_id = (
    SELECT dept.id
    FROM dept
    WHERE dept.name = '研发部'
);
-- 多表连接写法
SELECT emp.name
FROM emp
INNER JOIN dept
ON emp.dept_id = dept.id
WHERE dept.name = '研发部';

SELECT emp.*
FROM emp
WHERE emp.salary = (
    SELECT MAX(emp.salary)
    FROM emp
);

SELECT emp.*
FROM emp
INNER JOIN (
    SELECT emp.dept_id, MAX(emp.salary) AS max_sal
    FROM emp
    GROUP BY emp.dept_id
) AS temp
ON emp.dept_id = temp.dept_id
AND emp.salary = temp.max_sal;

SELECT dept.*
FROM dept
WHERE dept.id NOT IN (
    SELECT DISTINCT emp.dept_id
    FROM emp
    WHERE emp.dept_id IS NOT NULL
);