where 子句中的列“product_code”不明确[关闭]答案

【问题标题】：Column 'product_code' in where clause is ambiguous [closed]where 子句中的列“product_code”不明确[关闭]
【发布时间】：2017-09-14 12:32:33
【问题描述】：

    SELECT rm_item_cost.product_code, SUM(rm_item_cost.cost) AS rm_cost, SUM(dm_item_cost.cost) AS dm_cost, SUM(labour_item_cost.cost) AS labour_cost, SUM(overheads_item_cost.cost) AS o_cost 
FROM rm_item_cost 
INNER JOIN dm_item_cost ON dm_item_cost.product_code = rm_item_cost.product_code 
INNER JOIN labour_item_cost ON labour_item_cost.product_code = dm_item_cost.product_code 
INNER JOIN overheads_item_cost ON overheads_item_cost.product_code = labour_item_cost.product_code 
WHERE product_code = 'CMRO-01'

【问题讨论】：

消除歧义。否则，请参阅：Why should I provide an MCVE for what seems to me to be a very simple SQL query?
请提出问题，不要只发布代码
MySQL 'user_id' in where clause is ambiguous problem的可能重复

标签： mysql

【解决方案1】：

在您选择的表中，您有不止一个名为 product_code 的列，因此您必须添加一个别名来告诉 mysql 您指的是哪一列：

WHERE rm_item_cost.product_code = 'CMRO-01'

【讨论】：