左外部联接不起作用

问题描述

您好，我在下表中有-

tr_resource作为res-

tr_resource as res -

Resourceid  name
135021          ABC

tr_charac为chlev-

tr_charac as chlev -

characid   name
1          CH1
2          CH2

tr_characvalue作为cvlev-

tr_characvalue as cvlev -

characvalueid characid stringvalue
cv1             1       XX
cv2             2       YY
cv3             2       zz

tr_resourcecharac作为rchlev-

tr_resourcecharac as rchlev -

resourceid  characvalueid
135021          cv2

当我在查询下面运行时-

When i run below query -

select
    res.name,
    cvlev.stringvalue
from tr_resource res
    left outer join tr_resourcecharac rchlev on res.RESOURCEID = rchlev.RESOURCEID
    inner join tr_characvalue cvlev on  rchlev.CHARACVALUEID = cvlev.CHARACVALUEID
    inner join tr_charac chlev on chlev.CHARACID = cvlev.CHARACID and chlev.NAME = 'CH2'
 where res.resourceid=135021

我得到的答案是-

name  stringvalue
ABC      YY

但是当我在查询下面运行时，我没有得到任何答案-

but when i run below query, i am not getting any answer -

select
    res.name,
     cvlev.stringvalue
 from tr_resource res
     left outer join tr_resourcecharac rchlev on res.RESOURCEID = rchlev.RESOURCEID
     inner join tr_characvalue cvlev on  rchlev.CHARACVALUEID = cvlev.CHARACVALUEID
     inner join tr_charac chlev on chlev.CHARACID = cvlev.CHARACID and chlev.NAME = 'CH1'
 where res.resourceid=135021

我想以-

name  stringvalue
ABC      null

能请你帮忙吗?

推荐答案

您必须将所有内部联接更改为左侧外部联接.

You have to change all the inner joins to left outer joins.

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