T-SQL Case Statement in a JOIN ON Clause

Question

I am trying to build a case/if statement in a JOIN ON clause.

LEFT JOIN [CTSTRC] [Statuses] ON RIGHT([Statuses].[STRID], 3) = [CTE].[F61]
         


        

Answer 1

create a persisted computed column and add an index on it.

ALTER TABLE YourTable ADD
    NewIntID AS (CASE ISNUMERIC(RIGHT([Statuses].[STRID], 3) + '.0e0)
                     WHEN 1 THEN CAST(RIGHT([Statuses].[STRID], 3) AS INT) 
                     ELSE 0
                 END) PERSISTED
GO

CREATE INDEX IX_YourTable_NewIntID 
ON YourTable (NewIntID ); 
GO

you can now just join to the new NewIntID column as if it were the proper numeric ID now.