如果条件满足，则更新表.(将表b中的值更新为a)需要对应的值 [英] Update table if conditions met. (update the value from table b to a) corresponding value required

问题描述

我有一个表 a，其中包含字段日期"、时间"、成本和 order_id

I have a table a in which i have fields 'date', 'time', cost and order_id

表 b 包含字段 'year' 'month' 'hour' 'cost' 和 order_id 字段.

table b which has fields 'year' 'month' 'hour' 'cost' and order_id fields.

两个表都与order_id"字段相关联.如果两个表中的年、月、小时和 order_id 相同，我想更新表 a，并将表 b 中的相应值更新到表 a 字段成本"

both tables are linked with "order_id" field. i want to update table a if year, month, hour and order_id is same in both tables and update the corresponding value from table b to table a field "cost"

我用过这个语句，但是查询不起作用?它有什么问题?我需要帮助

I have used this statement, but query is not working? what is wrong in it? i need help

UPDATE item a, cost b
    SET a.cost = b.cost
    WHERE a.order_id = b.order_id
    AND YEAR(a.date) = b.YEAR
    AND month(a.date) = b.month
    AND hour(a.time) = b.hour

推荐答案

UPDATE item a
JOIN cost b ON a.order_id = b.order_id
           AND YEAR(a.date) = b.YEAR
           AND month(a.date) = b.month
           AND hour(a.time) = b.hour
SET a.cost = b.cost

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