T-SQL: Displaying data from multiple columns into one output column using CASE and COALESCE

Question

I have the following SQL code that runs against a Change Request database. Each record has several columns that represent affected US regions. If the change affects a region the value will be 1 otherwise NULL.

So I am adding the values in each column to determine if more than one region is affected, the answer will be greater than 1.

I need help in how to make a change to my COALESCE and/or CASE statements to list all affected areas that have a value of 1, in the "Affected_Area" output.

Affected Regions Last Seven Days

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SELECT ID, 
(ISNULL(southeast,0) + ISNULL(allregions,0) + ISNULL(midamerica,0)  + ISNULL(northcentral,0) + ISNULL(northeast,0) + ISNULL(pacificnorthwest,0) + ISNULL(pacificsouthwest,0)),
Affected_Area = COALESCE(
CASE WHEN [allregions]=1 THEN 'All Regions' ELSE NULL END,
CASE WHEN [midamerica]=1 THEN 'Mid-America' ELSE NULL END,
CASE WHEN [northcentral]=1 THEN 'North Central' ELSE NULL END,
CASE WHEN [northeast]=1 THEN 'Northeast' ELSE NULL END,
CASE WHEN [pacificnorthwest]=1 THEN 'Pacific Northwest' ELSE NULL END,
CASE WHEN [pacificsouthwest]=1 THEN 'Pacific Southwest' ELSE NULL END,
CASE WHEN [southeast]=1 THEN 'Southeast' ELSE NULL END
),
FROM [DB_Reporting].[dbo].change c with (nolock)
WHERE convert(varchar(10),([needed_by_date]),110) BETWEEN (DATEADD(DD,-7,CONVERT(VARCHAR(10),GetDATE(),110))) AND (DATEADD(DD,-1,CONVERT(VARCHAR(10),GetDATE(),110)))

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Any help is appreciated!

Hank Stallings

Answer 1

Try something like this:

SELECT ID, 
    (ISNULL(southeast,0) + ISNULL(allregions,0) + ISNULL(midamerica,0)  + ISNULL(northcentral,0) + ISNULL(northeast,0) + ISNULL(pacificnorthwest,0) + ISNULL(pacificsouthwest,0)),
    Affected_Area = 
        CASE WHEN [allregions]=1 THEN 'All Regions, ' ELSE '' END + 
        CASE WHEN [midamerica]=1 THEN 'Mid-America, ' ELSE '' END + 
        CASE WHEN [northcentral]=1 THEN 'North Central, ' ELSE '' END + 
        CASE WHEN [northeast]=1 THEN 'Northeast, ' ELSE '' END + 
        CASE WHEN [pacificnorthwest]=1 THEN 'Pacific Northwest, ' ELSE '' END + 
        CASE WHEN [pacificsouthwest]=1 THEN 'Pacific Southwest, ' ELSE '' END + 
        CASE WHEN [southeast]=1 THEN 'Southeast' ELSE '' END 
FROM [DB_Reporting].[dbo].change c with (nolock)
WHERE convert(varchar(10),([needed_by_date]),110) BETWEEN (DATEADD(DD,-7,CONVERT(VARCHAR(10),GetDATE(),110))) AND (DATEADD(DD,-1,CONVERT(VARCHAR(10),GetDATE(),110)))    

You'll likely need to trim a trailing comma.

Answer 2

Do you have any ability to change the design of this table? It seems less than correct - you'd be better with a region column with an FK off to a regions table. What will you do with the above if you have to add another region...

If you don't, you might want to use the PIVOT command and create a more normalised view that you can then use to query.