Question

I have a 2 tables:

  Questions table with Question ID

Part Table:

   Question ID
   Part ID
   BAllPartsRequired

The user will select some parts (or may select none) and depending on what was selected certain questions will be displayed.

I want to join the 2 tables for 3 scenerios but do them all in 1 query. I can write each scenerio individually (EDIT I thought I could but scenario 3 I can not get to work where it requires all found in part table to be selected) but can not figure out how to get them all in 1 query (I have done something similar before but cant remember how).

1. If no parts exist in part table for that question retruen the question

2. If any part selected exists in part table return question (i.e. user selects 1 part and 5 parts are associated to that question then the question will match and be returned). BAllPartsRequired = false

3. If user selects parts and ALL of the parts are associated to the question the question is returend but if NOT all parts are selected by user the question is not returend (i.e. user selects 3 parts and there are 4 parts in table then the user will not see the question, but if the user selectes all 4 parts the question will be shown). BAllPartsRequired = true

I am an advanced SQL programmer but this is eluding me and I know I have done this before but how do I get it to work in 1 query, do I do a nested join, a left join, a case on the where statement or something else.

Sample Data:

Question Form Association:          
NFormAssociationID  NQuestionID FormType    
1   1   PAEdit  
2   2   PAEdit  
3   3   PAEdit  
4   4   PAEdit  




Question Part Form Association Table:           
ID  NFormAssociationID  PartNumber  BAllPartsRequired
1   1   1   0
2   2   2   1
3   2   3   1

Query without the new parts table added:

Select ROW_NUMBER() OVER(ORDER BY QL.NOrderBy) AS RowNumber,
QL.NQuestionID, QL.FieldName, QL.Question, QL.BRequired, QFL.FormFieldType, QFL.SingleMultipleSM, 
QFL.CSSStyle
FROM dbo.QuestionFormAssociation QA WITH (NOLOCK)
INNER JOIN dbo.QuestionLookup QL WITH (NOLOCK) ON QA.NQuestionID = QL.NQuestionID
INNER JOIN dbo.QuestionFieldTypeLookup QFL WITH (NOLOCK) ON QL.NFieldTypeID = QFL.NFieldTypeID
WHERE QA.BActive = 1 AND QL.BActive = 1 AND QFL.BActive=1
AND QA.FormType = 'PAEdit'
ORDER BY QL.NOrderBy

Simple query using new table

Select ID
    FROM dbo.QuestionPartFormAssociation 
    WHERE BAllPartsRequired = 1 
    AND PartNumber IN ('1', '2') --'1', '2', '3')   

Answer 1

It sounds like you are trying to find the eligible questions, based on some criteria.

In this sitatuion, it is best to summarize first at the question level, and then apply logic to those summaries. Here is an example:

select q.questionid
from (select q.questionid,
             max(case when qp.questionid is null then 1 else 0 end) as HasNoParts,
             sum(case when qp.partid in (<user parts>) then 1 else 0 end) as NumUserParts,
             count(qp.questionid) as NumParts,
             max(qp.AllPartsRequired) as AreAllPartsRequired
      from question q left outer join
           questionpart qp
           on q.questionid = qp.questionid
      group by q.questionid
     ) q
 where HasNoParts = 1 or                                   -- condition 1
       AreAllPartsRequired = 0 and NumUserParts > 0 or     -- condition 2
       AreAllPartsRequired = 1 and NmUserParts = NumParts  -- condition 3

I’ve simplified the table and column names to make the logic clearer.

updated with full answer from OP:

Select ROW_NUMBER() OVER(ORDER BY QL.NOrderBy) AS RowNumber,
QL.NQuestionID, QL.FieldName, QL.Question, QL.BRequired, QFL.FormFieldType, QFL.SingleMultipleSM, 
QFL.CSSStyle
FROM dbo.QuestionFormAssociation QA WITH (NOLOCK)
INNER JOIN dbo.QuestionLookup QL WITH (NOLOCK) ON QA.NQuestionID = QL.NQuestionID
INNER JOIN dbo.QuestionFieldTypeLookup QFL WITH (NOLOCK) ON QL.NFieldTypeID = QFL.NFieldTypeID
INNER JOIN (
    select q.NFormAssociationID,
    max(case when qp.NFormAssociationID is null then 1 else 0 end) as HasNoParts,
    sum(case when qp.PartNumber in ('1','2','3') then 1 else 0 end) as NumUserParts,
    count(qp.NFormAssociationID) as NumParts, 
    qp.BAllPartsRequired
    from QuestionFormAssociation q 
    left outer join QuestionPartFormAssociation qp on q.NFormAssociationID = qp.NFormAssociationID      
        AND QP.BActive = 1  
    WHERE Q.FormType = 'PAEdit' 
    AND Q.BActive = 1   
    group by q.NFormAssociationID, qp.BAllPartsRequired

) QSUB ON QA.NFormAssociationID = QSUB.NFormAssociationID
WHERE QA.BActive = 1 AND QL.BActive = 1 AND QFL.BActive=1
AND (
    QSUB.HasNoParts = 1                                                     -- condition 1
    OR (QSUB.BAllPartsRequired = 0 and QSUB.NumUserParts > 0)               -- condition 2
    OR (QSUB.BAllPartsRequired = 1 and QSUB.NumUserParts = QSUB.NumParts)   -- condition 3
)
ORDER BY QL.NOrderBy