SQL Group By Join - sql

Question

I have three tables I need to join in order to tell what documents a product needs. Not all documents are needed on each product.
There is a Document table, a Product table, and a DocTracking table that tracks the documents associated with products
Product Table
ProdID ProdName
1 Ball
2 Wheel
DocTracking Table
ProdID DocID
1 1
1 2
2 2
I want the join to look like this:
ProdID ProdName Needs Word Doc? Needs Excel Doc?
1 Ball Yes Yes
2 Wheel No Yes
Any help would be appreciated, if I need to make this into a Stored Procedure, that is fine.

Answer 1

If you have only those documents and they are fix you can use this query:
SELECT ProdID, ProdName,
[Needs Word Doc] = CASE WHEN EXISTS(
SELECT 1 FROM Document d INNER JOIN DocTracking dt ON d.DocID=dt.DocID
WHERE dt.ProdID = p.ProdID AND d.[Doc Name] = 'Word Document'
) THEN 'Yes' ELSE 'No' END,
[Needs Excel Doc] = CASE WHEN EXISTS(
SELECT 1 FROM Document d INNER JOIN DocTracking dt ON d.DocID=dt.DocID
WHERE dt.ProdID = p.ProdID AND d.[Doc Name] = ' Excel Spreadsheet'
) THEN 'Yes' ELSE 'No' END
FROM dbo.Product p
Of course you could also use the DocID, then the query doesn't depend on the name.

Answer 2

select P.ProdID, P.ProdName,
case
when DW.DocID is null then 'Yes'
else 'No'
end as NeedsWordDoc,
case
when DE.DocID is null then 'Yes'
else 'No'
end as NeedsExcelDoc
from Product P
left join DocTracking DTW on DTW.ProdId = P.ProdId
left join Document DW on DW.DocID = DTW.DocID
and DW.Name = 'Word Document'
left join DocTracking DTE on DTE.ProdId = P.ProdId
left join Document DE on DE.DocID = DTE.DocID
and DE.Name = 'Excel Spreadsheet'

Answer 3

This is a little more complicated than a typical pivot query. But, the only challenging part is determining which documents are included, and then getting 'Yes' or 'No' out.
The following does this with coalesce() and a conditional that checks for the presence of one type of document:
select pt.ProdId, pt.ProdName,
coalesce(MAX(case when dt.DocId = 1 then 'Yes' end), 'No') as "Needs Word Doc?",
coalesce(MAX(case when dt.DocId = 2 then 'Yes' end), 'No') as "Needs Excel Doc?"
from ProductTable pt left outer join
DocTracking dt
on dt.ProdId = dt.ProdId
group by pt.ProdId, pt.ProdName;
Note that SQL queries return a fixed number of columns. So, you cannot have a SQL query that simply returns a different number of columns based on what is present in the documents table. You can create a SQL query in a string and then use a database-specific command to run it.

Answer 4

may be this would help you - using pivot:
select ProdId, ProdName,
case when isnull([Word Document],0)<>0 then 'Yes'
else 'No'
end as [Needs Word Doc?],
case when isnull([Excel Spreadsheet],0)<>0 then 'Yes'
else 'No'
end as [Needs Excel Spreadsheet?]
from
(
select p.ProdId,p.ProdName,d.DocId,d.DocName from
#Prod p left join
#Track t
on p.ProdId=t.ProdId
inner join #Doc d
on t.DocId=d.DocId
)
as temp
pivot
(max(DocID)
For DocName in ([Word Document],[Excel Spreadsheet])
)
as pvt