SQL SELECT多个表中检索 


来自多个表的SQL SELECT

该语句用于从多个表中检索字段。为此,我们需要使用联接查询从多个表中获取数据。

让我们看一下从多个表中进行选择的示例:

SELECT orders.order_id, suppliers.name 
FROM suppliers
INNER JOIN orders
ON suppliers.supplier_id = orders.supplier_id
ORDER BY order_id;

让我们拿三个表,两个名为customer1和customer2的客户表,第三个表是product表。

客户1表

Cus_id Name1
1 Jack
2 Jill

Customer2表

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

从多个表中选择的示例语法:

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
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
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