更新一个表中某个字段的所有记录，该字段的值仅在另一个表中

Question

我有表A：

+---------------+------------+-------+-------------+
| name          | id_product | price | price_medium|
+---------------+------------+-------+-------------+
| phone         |         1  |   300 |         300 |
| mouse         |         2  |    50 |          75 |
| phone         |         1  |   250 |         300 |
| keyboard      |         3  |   100 |         100 |
| mouse         |         2  |   100 |          75 |
| phone         |         1  |   350 |         300 |
+---------------+------------+------+--------------+

表B是一个临时表，每次购买时添加产品然后删除。 发送时，我想在表 A 中更新表 B 中的列“price_medium”，其 product_id 是添加项。

+---------------+------------+-------+-------------+
| name          | id_product | price | price_medium|
+---------------+------------+-------+-------------+
| phone         |         1  |   100 |         220 |
| mouse         |         2  |   125 |          92 |
| phone         |         1  |   100 |         220 |
+---------------+------------+------+--------------+

最终结果将在表 A 中

+---------------+------------+-------+-------------+
| name          | id_product | price | price_medium|
+---------------+------------+-------+-------------+
| phone         |         1  |   300 |         220 |
| mouse         |         2  |    50 |          92 |
| phone         |         1  |   250 |         220 |
| keyboard      |         3  |   100 |         100 |
| mouse         |         2  |   100 |          92 |
| phone         |         1  |   350 |         220 |
+---------------+------------+------+--------------+

Answer 1

• 您可以使用id_product在两个表之间进行Inner Join
• 使用Set更新 tableA 中的price_medium （等于 tableB 中的price_medium ）

尝试：

UPDATE tableA AS tA
JOIN tableB AS tB ON tB.id_product = tA.id_product 
SET tA.price_medium = tB.price_medium