mysql如何拼接表

| id | name  | department_id |
|----|-------|---------------|
| 1  | Alice | 1             |
| 2  | Bob   | 2             |
| 3  | Carol | 1             |

| id | name      |
|----|-----------|
| 1  | HR        |
| 2  | Engineering|

SELECT employees.name AS employee_name, departments.name AS department_name
FROM employees
JOIN departments ON employees.department_id = departments.id;

+-------------+----------------+
| employee_name | department_name |
+-------------+----------------+
| Alice       | HR             |
| Bob         | Engineering    |
| Carol       | HR             |
+-------------+----------------+

| product | sales |
|---------|-------|
| A       | 100   |
| B       | 200   |

| product | sales |
|---------|-------|
| A       | 150   |
| C       | 300   |

SELECT product, sales FROM sales_2023
UNION
SELECT product, sales FROM sales_2024;

+---------+-------|
| product | sales |
+---------|-------|
| A       | 100   |
| B       | 200   |
| A       | 150   |
| C       | 300   |
+---------+-------|

SELECT product, SUM(sales) AS total_sales
FROM (
    SELECT product, sales FROM sales_2023
    UNION ALL
    SELECT product, sales FROM sales_2024
) AS combined_sales
GROUP BY product
HAVING total_sales > 1000;