SQL Server Self Joins

Hi,

I have a table called Test with columns questionid,text,qid

basically qid also a questionid which is a help text for the main question. questions
which does not have help text will have qid as NULL

now i want to retrive all questionid's with the question text but those questions which has
qid I want that text for qid in the same row . so basically I want the question text and the  qid
text (help text) in the same row for each questionid. for those questions where qid is null should return null. and I dont want the qid questionid's appearing as seperate questions in my result sets.

Example

questinid   text                         qid
101         what is ur name ?     102
102         this is mandatory       null
103         DOB                             null

so my result set should be like below :

questionid   text                        helptext
101          What is ur name ?    this is mandatory
103          DOB                           null



can some one please advise me the best query for this ?

Many Thanks
gvamsimbaAsked:
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Vitor MontalvãoMSSQL Senior EngineerCommented:
Try this one:
SELECT T1.questinid, T1.text, T2.text helptext
FROM Test T1
LEFT OUTER JOIN Test T2 ON T1.qid=T2.questinid
WHERE NOT EXISTS (SELECT 1 FROM Test T3 WHERE T1.questinid=T3.qid)

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John_VidmarCommented:
Similar solution to Vitor, but eliminates the correlated sub-query:
SELECT	T1.questinid
,	T1.text
,	T2.text helptext
FROM	Test T1
LEFT
JOIN	Test T2			ON	T1.qid = T2.questinid
LEFT
JOIN	Test T3			ON	T1.qid = T3.questinid
WHERE	T3.questinid IS NULL

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gvamsimbaAuthor Commented:
Hi John , your join condition on t3 is incorrect. the below will work...


SELECT      T1.questinid
,      T1.text
,      T2.text helptext
FROM      Test T1
LEFT
JOIN      Test T2                  ON      T1.qid = T2.questinid
LEFT
JOIN      Test T3                  ON      T1.questinid = T3.qid
WHERE      T3.questinid IS NULL
gvamsimbaAuthor Commented:
Excellent
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Microsoft SQL Server 2008

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