SQL Server 中带有 JOIN 的 UPDATE 语句未按预期工作答案

【问题标题】：UPDATE statement with JOIN in SQL Server Not Working as ExpectedSQL Server 中带有 JOIN 的 UPDATE 语句未按预期工作
【发布时间】：2021-02-09 21:52:00
【问题描述】：

我正在尝试将VEHICLES_FW 表中所有记录的LAST_INSPECTION_FW 字段更新为最后一个JOB_DATE_FW 以用于REASON_CODE_FW = 35 的记录。但是，发生的情况是，一旦执行了以下代码，它就没有考虑到 WHERE 子句。这会导致所有记录都更新，而它应该只更新带有REASON_CODE_FW = 35 的记录。

有没有办法重组此代码以使其正常工作？请帮忙，谢谢！

UPDATE VEHICLES_FW
 SET VEHICLES_FW.LAST_INSPECTION_FW = JOB_HEADERS_FW.FIELD2MAX
FROM VEHICLES_FW
INNER JOIN (SELECT VEHICLE_ID_FW, MAX(JOB_DATE_FW) AS FIELD2MAX
FROM JOB_HEADERS_FW
GROUP BY VEHICLE_ID_FW) AS JOB_HEADERS_FW
ON VEHICLES_FW.VEHICLE_ID_FW = JOB_HEADERS_FW.VEHICLE_ID_FW
INNER JOIN JOB_DETAILS_FW
ON JOB_NUMBER_FW = JOB_NUMBER_FW
WHERE REASON_CODE_FW = '35'

【问题讨论】：

您好 Wayne，我建议您在查询中开始使用表别名，以便在引用列时清楚该列来自哪个表。另外，INNER JOIN JOB_DETAILS_FW ON JOB_NUMBER_FW = JOB_NUMBER_FW 可能不是您想要的？

标签： sql sql-server tsql join sql-update

【解决方案1】：

Common Table Expressions 是您的朋友。 SQL Server 的奇怪 UPDATE ... FROM 语法不是。 EG

with JOB_HEADERS_FW_BY_VEHICLE_ID as
(
  SELECT VEHICLE_ID_FW, MAX(JOB_DATE_FW) AS FIELD2MAX
  FROM JOB_HEADERS_FW
  GROUP BY VEHICLE_ID_FW
), q as
(
Select VEHICLES_FW.LAST_INSPECTION_FW, JOB_HEADERS_FW_BY_VEHICLE_ID.FIELD2MAX NEW_LAST_INSPECTION_FW
FROM VEHICLES_FW
INNER JOIN   JOB_HEADERS_FW_BY_VEHICLE_ID 
  ON VEHICLES_FW.VEHICLE_ID_FW = JOB_HEADERS_FW_BY_VEHICLE_ID.VEHICLE_ID_FW
INNER JOIN JOB_DETAILS_FW
  ON JOB_NUMBER_FW = JOB_NUMBER_FW
  WHERE REASON_CODE_FW = '35'
)
UPDATE q set LAST_INSPECTION_FW = NEW_LAST_INSPECTION_FW

【讨论】：

【解决方案2】：

我怀疑这是你想要的：

update v
set last_inspection_fw = (
    select max(j.job_date_fw)
    from job_headers_fw j
    inner join job_details_fw jd on jd.job_number_fw = j.job_number_fw
    where j.vehicle_id_fw = v.vehicle_id_fw and jd.reason_code_fw = 35
)
from vehicles_fw v

【讨论】：