sql - 用于比较结果的 SQL 命令不起作用

Question

我有下面的代码工作并带回 OEMPartNumber。我的问题是 OEMSubNumber。正如您在表中看到的那样，我无法像我在 sql 中所做的那样匹配 OEMSubNumber。我必须将 OEMSubNumber 与 OEMPartNumber 匹配，然后返回 OEM 项目。我该怎么做？

正在工作的sql

UPDATE a 
SET a.AMIPartNumber = c.Item 
FROM imports as a 
INNER JOIN jdsubs as b 
ON a.OEMPartNumber = b.OEMPartNumber 
INNER JOIN amipartnumbers as c 
ON b.OEMPartNumber = c.OEMItem

这是我的表格布局

imports
----------------
OEMPartNumber  | AMIPartNumber
AR77530        |
AR12345        |

JDSubs
---------------------------
OEMPartNumer    | OEMSubNumber
AR65123         | AR77530
AR12345         | AR56242

AMI
---------------------------
Item            | OEMItem   | Description
AMAR65123       | AR65123   | Axle
AMAR56242       | AR12345   | Spindle

更新

我把这个工作得很好！

UPDATE imports
SET imports.AMIPartNumber = coalesce(apn.Item,asn.Item)
FROM imports as I 
LEFT JOIN jdsubs as PN          ON I.OEMPartNumber = PN.OEMPartNumer 
LEFT JOIN amipartnumbers as APN ON PN.OEMPartNumer = APN.OEMItem 
LEFT JOIN jdsubs as SN          ON I.OEMPartNumber = SN.OEMSubNumber 
LEFT JOIN amipartnumbers as ASN ON SN.OEMPartNumer = ASN.OEMItem
;

select
*
from imports