MySQL 无法在 FROM 多个表连接中指定要更新的目标表

Posted 2023-02-24

【中文标题】MySQL 无法在 FROM 多个表连接中指定要更新的目标表

【英文标题】：MySQL can’t specify target table for update in FROM multiple table joins

【发布时间】：2016-07-03 06:01:31

【问题描述】：

我已经搜索了好几天，以了解如何在尝试更新多连接表中的字段时解决此错误，并使用同一多连接表集中的最短日期。

这是我的更新声明：

update vtiger_projectmilestone 
Inner Join vtiger_projectmilestonecf  ON vtiger_projectmilestone.projectmilestoneid = vtiger_projectmilestonecf.projectmilestoneid
Inner Join vtiger_crmentity ON vtiger_projectmilestone.projectmilestoneid = vtcrmm.crmid
inner join vtiger_project on vtiger_project.projectid = vtiger_projectmilestone.projectid
Inner Join vtiger_crmentity vtcrmp ON vtcrmp.crmid = vtiger_project.projectid

 set vtiger_projectmilestone.projectmilestonedate =
(select min(vtiger_projecttaskcf.cf_779) 
FROM vtiger_projecttask tvpt
Inner Join vtiger_projecttaskcf tvptcf ON tvpt.projecttaskid  = tvptcf.projecttaskid
Inner Join vtiger_projectmilestone tvpm ON tvpm.projectmilestoneid = tvpt.projecttasknumber
Inner Join vtiger_projectmilestonecf vtpmcf ON tvpm.projectmilestoneid = tvpmcf.projectmilestoneid
Inner Join vtiger_crmentity AS vtcrmm ON tvpm.projectmilestoneid = vtcrmm.crmid
Inner Join vtiger_crmentity AS vtcrmt ON tvpt.projecttaskid = vtcrmt.crmid
where tvpm.projectmilestone_no = vtiger_projectmilestone.projectmilestone_no
) 
where vtiger_projectmilestone.projectid = 
(select vtiger_project.projectid from vtiger_project 
INNER JOIN vtiger_crmentity vtcrmp ON vtiger_project.projectid = vtcrmp.crmid
where vtcrmp.deleted = 0 order by vtiger_project.projectid desc limit 1)
and vtcrmp.deleted = 0
and vtcrmm.deleted = 0 
and (vtiger_projectmilestone.projectmilestonedate is null or      vtiger_projectmilestonecf.cf_763 is null) ;

这是一个真实的更新查询，而不仅仅是一个简单的表关系。

我通过创建一个临时表、插入值、更新目标表和删除临时表来解决这个问题。

我真的很想解决这个问题，因为它会更频繁地出现。

感谢所有帮助。

干杯 伯纳德·贝利

【参考方案1】：

正如this answer 中所述，您不能在子查询中使用目标更新表，正如您在查询中看到的那样

SELECT min(vtiger_projecttaskcf.cf_779) 
FROM vtiger_projecttask tvpt
Inner Join vtiger_projecttaskcf tvptcf ON tvpt.projecttaskid  = tvptcf.projecttaskid
Inner Join 
--using target update table in query
vtiger_projectmilestone tvpm ON tvpm.projectmilestoneid = tvpt.projecttasknumber 
Inner Join vtiger_projectmilestonecf vtpmcf ON tvpm.projectmilestoneid = tvpmcf.projectmilestoneid
Inner Join vtiger_crmentity AS vtcrmm ON tvpm.projectmilestoneid = vtcrmm.crmid
Inner Join vtiger_crmentity AS vtcrmt ON tvpt.projecttaskid = vtcrmt.crmid
where tvpm.projectmilestone_no = vtiger_projectmilestone.projectmilestone_no

但是我认为解决方法是使用您正在更新的表中的数据，因此您可以编写一些 where 条件，而不是使用连接，例如：

SELECT min(vtiger_projecttaskcf.cf_779) 
FROM vtiger_projecttask tvpt
Inner Join vtiger_projecttaskcf tvptcf ON tvpt.projecttaskid  = tvptcf.projecttaskid 
Inner Join vtiger_projectmilestonecf vtpmcf ON tvpm.projectmilestoneid = tvpt.projecttasknumber
Inner Join vtiger_crmentity AS vtcrmm ON tvpt.projecttasknumber = vtcrmm.crmid
Inner Join vtiger_crmentity AS vtcrmt ON tvpt.projecttaskid = vtcrmt.crmid
where tvpm.projectmilestone_no = vtiger_projectmilestone.projectmilestone_no
--using the projectmilestoneid in a where clause
AND tvpt.projecttasknumber=vtiger_projectmilestone.projectmilestoneid 

需要注意的是，您可能会遇到一些性能问题，此外，由于我不知道完整的架构，我无法判断在子查询中使用其他表而不是 vtiger_projectmilestone 是否会给您正确的结果