MySQL之使用WITH子句和临时表达式进行数据分析和筛选方式

WITH my_cte AS (
    SELECT 
        column1,
        column2
    FROM 
        my_table
    WHERE 
        condition
)
SELECT 
    *
FROM 
    my_cte
WHERE 
    column1 > 10;

CREATE TABLE employee (
    emp_id INT,
    emp_name VARCHAR(50),
    emp_salary DECIMAL(10, 2),
    department_id INT
);

INSERT INTO employee VALUES
(1, 'John Doe', 50000.00, 1),
(2, 'Jane Smith', 60000.00, 2),
(3, 'Bob Johnson', 75000.00, 1),
(4, 'Alice Williams', 80000.00, 2);

WITH department_avg_salary AS (
    SELECT
        department_id,
        AVG(emp_salary) AS avg_salary
    FROM
        employee
    GROUP BY
        department_id
)
SELECT
    e.emp_id,
    e.emp_name,
    e.emp_salary,
    e.department_id
FROM
    employee e
JOIN
    department_avg_salary d ON e.department_id = d.department_id
WHERE
    d.avg_salary > (SELECT AVG(emp_salary) FROM employee);

+--------+----------------+------------+---------------+
| emp_id | emp_name       | emp_salary | department_id |
+--------+----------------+------------+---------------+
|      3 | Bob Johnson    |   75000.00 |             1 |
|      4 | Alice Williams |   80000.00 |             2 |
+--------+----------------+------------+---------------+