不了解 sql 连接上的相关名称答案

【问题标题】：Not understanding correlation names on sql joins不了解 sql 连接上的相关名称
【发布时间】：2014-10-28 21:08:54
【问题描述】：

有人可以向我解释如何在此联接中关联这些名称吗？当我执行时，我收到错误消息说 From 子句中的对象具有相同的公开名称

select
inv_mast.item_id as Item,
inv_loc.location_id as location,
company.company_name as company,
vendor_supplier.vendor_id as vendorID
from
inv_loc
join inv_mast on inv_mast.inv_mast_uid = inv_loc.inv_mast_uid 
join inv_loc on company.company_id = inv_loc.company_id 
JOIN company ON (company.company_id = vendor_supplier.company_id)

【问题讨论】：

您在from 和join 中使用inv_loc，但您没有给它们任何别名，所以当您说：inv_loc.company_id SQL Server 不知道哪个一个你想要的
你为什么要加入2次inv_loc表？你可以加入1次，有2个条件

标签： sql sql-server database join sql-server-2012

【解决方案1】：

你加入inv_loc 两次 - 你要么需要修复你的加入，要么引入一个别名，比如：

select      inv_mast.item_id as Item,
            mast.location_id as MasterLocation,
            companylocation.location_id as CompanyLocation,
            company.company_name as company,
            vendor_supplier.vendor_id as vendorID

from        inv_loc AS mast

join        inv_mast 
    on      inv_mast.inv_mast_uid = mast.inv_mast_uid 

join        inv_loc AS companylocation
    on      company.company_id = companylocation.company_id 

JOIN        company 
    ON      company.company_id = vendor_supplier.company_id

【讨论】：