Parse comma separated value and map with other table to get Name and change it back to comma separate.

Question

Hi,
I have one existing view(with around 15 fields), in which I have to add few more fields from table called PI.
Now these fields have values like (55C4444F-D83B-4F96-A011-367A3755BA6C , F52388E2-485B-49DF-8534-FDF46D23F59E , 722432E1-F063-4CBD-B83D-1B97836E82953) 3 values comma separated.(Sometimes only one value and sometimes 4 or 5 or 7-8 depend on user has entered
on web page)
Also I have another table called PHA and this tables has 2 fields Values and Name so I have to map this two tables based on VALUES fields and get Name from this PHA table and show in view and that also Comma separated.
So basically I have to Parse the PI table's Values field 1st, map it with PHA table to get Name and then Make it comma separated in that existing view.
To make fields comma separate I used below query,
(SELECT DISTINCT SUBSTRING
            SELECT ','+ PI.[Name]  AS [text()]
            FROM [DB].[dbo].[Table] PHA1
Inner Join  [DB].[dbo].[Table] PI
ON PHA.[Value] = PI.[VALUE]
            WHERE PHA1.PId =PHA2.PId and PHA1.CId = PHA2.CId
            ORDER BY PHA1.PId
            For XML PATH ('')
        ), 2, 1000) 
FROM [DB].[dbo].[Table] PHA2
Inner Join [cSharpSite_profiles].[dbo].[PetAllergies] PA
Inner Join  [DB].[dbo].[Table] PI
ON PHA.[Value] = PI.[VALUE]
) [Name]
Vicky

Answer 1

Wait, this sounds wrong. You have a view where you group values into a comma-separated list. While that surely will make some purists cringe, I can see that it makes sense from a presentation perspective.
But if you want to use these concatenated values as atomic values again, you should go back to the base tables and them from there. Building views on views may sometimes be a good idea, but if you are too keen on reuse you can cause a performance disaster.
So do it right from the beginning.
Erland Sommarskog, SQL Server MVP, [email protected]