Question

我想知道如果product_id在其他表中没有分配任何category_id，我可以将产品状态更改为0。

+------------+----------+  +------------+-------------+
| Product_id |  Status  |  | Product_id | cateogry_id |
+------------+----------+  +------------+-------------+
|      1     |     1    |  |     1      |      10     |
|      2     |     1    |  |     3      |      20     |
|      3     |     1    |  +------------+-------------+
+------------+----------+

结果我需要没有类别状态的product_id = 2为0。是否有一个MySQL查询？

Answer 1

首先，您需要获取表中不存在的行..

table1是状态为
的表 table2是类别为id

的表

           table1                     table2
+------------+----------+  +------------+-------------+
| Product_id |  Status  |  | Product_id | cateogry_id |
+------------+----------+  +------------+-------------+
|      1     |     1    |  |     1      |      10     |
|      2     |     1    |  |     3      |      20     |
|      3     |     1    |  +------------+-------------+
+------------+----------+

所以现在运行此查询以获取没有category_id的行

SELECT product_id 
FROM table1 t
LEFT JOIN table2 t2 ON t2.product_id = t.product_id
WHERE t2.product_id IS NULL

现在像这样更新table1

UPDATE table1 t,
(   SELECT product_id 
    FROM table1 t
    LEFT JOIN table2 t2 ON t2.product_id = t.product_id
    WHERE t2.product_id IS NULL
) t1
SET t.status = 0
WHERE t1.product_id = t.product_id

DEMO

Answer 2

您可以在更新中使用左连接，其中包含null

update product p
left join product_relation pr on (p.Product_id = pr.Product_id)
set p.Status = 0
where pr.Product_id is null

Demo

Answer 3

或者更简单..如果在table2中根本找不到它：

Update table1
Set status = 0
Where Product_id not in (SELECT Product_id FROM table2)

MYSQL更新连接为空

3 个答案: