如何从一个表中获取所有记录，仅从连接表中获取具有条件的记录

Question

it seems like I've accomplished this before, but struggling again. Here is my data:

tblHotlist
----------
ID
hotlistStatus
buildNumber
loadType
etc

tblessr
-------
ID
esHeadline
notesStatus
actionItems
bugStatusID
etc

tblBugStatus (not needed in query)
------------
ID
bugStatus
etc

tbl_j_hlbug
-----------
esID
hotlistID
timestamp

I want all the records from tblHotlist and if records exist in tblESSR, I need those where bugStatusID=300. I've tried several different joins and subqueries, but still can't get the results I need. Once I put the qualifier of bugStatusID=300, I only get the records from tblHotlist where records from tblESSR has a bugStatusID of 300.

failed attempt:

SELECT hl.hotlistID, hl.buildnumber, es.ID, es.notesStatus, es.actionItems
FROM tblhotList hl
     LEFT OUTER JOIN tbl_j_hlbug j ON j.hotlistID = hl.id
     LEFT OUTER JOIN tblESSR es ON j.esrID = es.id
WHERE hl.hotlistStatusID=100 AND hl.loadType='su' AND es.bugStatusID=300

Any help would be appreciated. I've tried different joins and a couple of subqueries, but I always get the same result.

Thanks!

Answer 1

Because of the join, some of your result set BEFORE the WHERE will have NULL in bugStatusID, so you need to add this into your where if you wish to see those results as well.

SELECT hl.hotlistID, hl.buildnumber, es.ID, es.notesStatus, es.actionItems
FROM tblhotList hl
     LEFT OUTER JOIN tbl_j_hlbug j ON j.hotlistID = hl.id
     LEFT OUTER JOIN tblESSR es ON j.esrID = es.id
WHERE hl.hotlistStatusID=100 AND hl.loadType='su' AND (es.bugStatusID=300  OR es.bugStatusID IS NULL)

Answer 2

You either have to move the limiting criteria to the joins or also look for null values.

WHERE hl.hotlistStatusID=100 AND hl.loadType='su' AND 
(es.bugStatusID=300 or es.bugStatusID is null)

When the outer joins occur, you have to consider null values will exist on records that don't have matching data. As such if you try to limit by these, you will end up excluding the nulls w/o matching data; thereby negating the outer join. Sometimes this is what you want... sometimes it isn't. In this case I think you wanted the nulls and 300.

SELECT hl.hotlistID, hl.buildnumber, es.ID, es.notesStatus, es.actionItems
FROM tblhotList hl
     LEFT OUTER JOIN tbl_j_hlbug j ON j.hotlistID = hl.id
     LEFT OUTER JOIN tblESSR es 
        ON j.esrID = es.id
       AND es.bugStatusID=300
WHERE hl.hotlistStatusID=100 AND hl.loadType='su' 

the Hl where clause doesn't matter as you're getting all records to begin with.