极客笔记SQL 多表SELECT
此语句用于从多个表中检索字段。为此，我们需要使用连接查询来从多个表中获取数据。
让我们看一个从多个表选择的例子：
SELECT orders.order_id, suppliers.name
FROM suppliers
INNER JOIN orders
ON suppliers.supplier_id = orders.supplier_id
ORDER BY order_id;
让我们来看看三个表，两个名为customer1和customer2的客户表，还有第三个表是产品表。
Customer1表
| Cus_id | Name1 |
|---|---|
| 1 | Jack |
| 2 | Jill |
顾客2表格
| Cus_id | Name2 |
|---|---|
| 1 | Sandy |
| 2 | Venus |
产品表
| P_id | Cus_id | P_name |
|---|---|---|
| 1 | 1 | Laptop |
| 2 | 2 | Phone |
| 3 | P1 | Pen |
| 4 | P2 | Notebook |
选择多个表格的示例语法：
SELECT p. p_id, p.cus_id, p.p_name, c1.name1, c2.name2
FROM product AS p
LEFT JOIN customer1 AS c1
ON p.cus_id=c1.cus_id
LEFT JOIN customer2 AS c2
ON p.cus_id = c2.cus_id
| 暂无内容 P_id | Cus_id | P_name | P_name | P_name |
|---|---|---|---|---|
| 1 | 1 | Laptop | Jack | NULL |
| 2 | 2 | Phone | Jill | NULL |
| 3 | P1 | Pen | NULL | Sandy |
| 4 | P2 | Notebook | NULL | Venus |