Question

I have a stored procedure like this (shortened to the minimum necessary):

CREATE PROCEDURE [dbo].[proc_Foo]
    -- Add the parameters for the stored procedure here
    @StyleNumber int,
    @App nvarchar(50),
    @User nvarchar(20)
AS
BEGIN
    DECLARE @UserChar varchar(1) = 'U'

    -- User with App
    SELECT [StyleType],
           [Value], 'UA' AS 'DerivedFrom'
    FROM daten.dbo.GridStyleLocal
    WHERE [StyleAssign] = @UserChar
    AND [User] = @User
    AND [StyleNumber] = @StyleNumber
    AND [Application] = @App

    UNION

    -- Global (Basis) with app
    SELECT [StyleType],
           [Value], 'GA' AS 'DerivedFrom'
    FROM basis.dbo.GridStyle
    WHERE [StyleNumber] = @StyleNumber
    AND [Application] = @App
    AND [StyleType] NOT IN (
        SELECT [StyleType]
        FROM daten.dbo.GridStyleLocal
        WHERE [StyleAssign] = @UserChar
        AND [User] = @User
        AND [StyleNumber] = @StyleNumber
        AND [Application] = @App)

    UNION

    -- Scrape missing StyleTypes from Number 0
    SELECT [StyleType],
           [Value], 'G0A' AS 'DerivedFrom'
    FROM basis.dbo.GridStyle
    WHERE [StyleNumber] = 0
    AND [Application] = @App
    AND [StyleType] NOT IN (
        SELECT [StyleType]
        FROM daten.dbo.GridStyleLocal
        WHERE [StyleAssign] = @UserChar
        AND [User] = @User
        AND [StyleNumber] = @StyleNumber
        AND [Application] = @App)
    AND [StyleType] NOT IN (
        SELECT [StyleType]
        FROM basis.dbo.GridStyle
        WHERE [StyleNumber] = @StyleNumber
        AND [Application] = @App)

END

GO

Now StyleNumber 0 is my base style. All properties (StyleType) that are not in another StyleNumber are derived from StyleNumber 0. But now if I include the second SELECT (Global (Basis) with app) when @StyleNumber is set to 0, the DerivedFrom value is GA instead of G0A.

So is there a any kind of conditional, that could exclude this SELECT out of the union if @StyleNumber is 0?

Answer 1

Not very clear exactly what you need. Assuming you need to get G0A if @StyleNumber = 0 from the second query, change your second select query (– Global (Basis) with app) as follows with the CASE.

SELECT [StyleType],
       [Value], 
       CASE @StyleNumber WHEN 0 THEN 'G0A' ELSE 'GA' END AS 'DerivedFrom'
FROM basis.dbo.GridStyle
--Rest fo the query

NOT to select any records from second select query if @StyleNumber = 0, add CASE to WHERE clause as;

WHERE [Application]  = 
  CASE @StyleNumber
      WHEN 0 THEN 'This app does not exist' --Give unavailable @App number 
      ELSE @App
  END