SQL连接两个表与LEFTJOIN

Question

我有表

• table_order
• PRODUCT_NAME

下面是SQL我要查询table_order这在输出的product_id完美的作品，但我需要它显示它的名字而不是数字。我需要用LEFTJOIN来修改mySQL，以某种方式连接到表product_name，但我不断收到错误。因此，而不是

99 = 15，99 = 16

我需要

99 =名称1，99 = NAME2

SELECT table_order.order_id, table_order.product_id 
       FROM table_order 
       WHERE table_order.order_id=99 
       ORDER BY table_order.order_product_id 


table table_order 
_________________________ 
order_id | product_id | 
_________________________ 
99  | 15   | 
99  | 16   | 
_________________________ 

table product_name 
___________________________ 
product_id | product_name | 
___________________________ 
15   | name1  | 
16   | name2  | 
___________________________ 

Answer 1

您需要像product_id那样加入表格。

SELECT table_order.order_id, product_name.product_name 
FROM table_order 
    INNER JOIN product_name on table_order.product_id = product_name.product_id 
WHERE table_order.order_id=99 
ORDER BY table_order.product_id 

Answer 2

使用

SELECT a.product_id, b.product_name 
    FROM table_order AS a LEFT JOIN product_name AS b ON a.product_id = b.product_id 
    WHERE a.order_id = '99' 
    ORDER BY a.product_id 

Answer 3

Select t1.product_id,t2.product_name from table_order as t1 
    inner join(
    select * from product_name 
) as t2 
    on t1.product_id = t2.product_name 
    where t1.product_id = //some Number 

见如果有效的话。

Answer 4

如果您需要输出所有订单，无论该table_order的产品ID是否与product_table有连接，则需要使用LEFT JOIN。

SELECT o.order_id, p.product_name 
    FROM table_order o 
     LEFT JOIN product_name p ON o.product_id = p.product_id 
    ORDER BY o.product_id 

但是如果你只需要得到存在两个表中的所有行，你可以使用一个INNER JOIN

SELECT o.order_id, p.product_name 
    FROM table_order o 
     INNER JOIN product_name p ON o.product_id = p.product_id 
    ORDER BY o.product_id