SQL dynamic unpivot table as function - sql

Question

I currently have a query which I am using to unpivot an existing table.
Some background information on the table - each year a new column is added to the table to indicate the $ values for a project ID for that year. With every column added one will be dropped. All these columns are prefixed with 'YR_' followed by the new year. There are constantly 20 'YR_' columns.
I am required to unpivot the 'YR_' columns so that they appear as per below, allowing me to utilize the information easier for several reports -
Before unpivot -
ProjectID YR_16 YR_17 YR_18 YR_19 YR_20
10 0 100 20 25 100
After unpivot -
ProjectID YR Value
10 YR_16 0
10 YR_17 100
10 YR_18 20
10 YR_19 25
10 YR_20 100
Below is the query I am using to create the unpivot table, which will dynamically pick up columns as they are added/dropped
declare #query as NVARCHAR(max);
Declare #cols as NVARCHAR(250) = STUFF((
Select distinct ',' + QUOTENAME(Column_Name)
From INFORMATION_SCHEMA.COLUMNS
where TABLE_NAME = 'F1BWK_PLM_CAPEX'
And COLUMN_NAME like 'YR_%'
For XML Path(''), type)
.value('.','NVARCHAR(MAX)')
,1,1,'');
Select #query = 'With Unpivoted as
(
Select * from F1BWK_PLM_CAPEX U
Unpivot (
Val
For Yr in (' + #cols + ')
)
As UnpivotTable
)
Select U.*
From Unpivoted U
inner join [dbo].[F1_SYPAR_CTL] CTL
on CTL.value = U.WS_VERS
and CTL.PARAM_NAME like ''MBRC_CURR_PLM_BUDVER''
inner join [dbo].[F1_SYPAR_CTL] CTL2
on CTL2.value = U.WS_NAME
and CTL2.PARAM_NAME like ''MBRC_CURR_PLM_BUDWSH''';
Exec(#query);
I am having issues in turning this query into a function so that I can call upon it and save it in SQL Server so that other members of my team can use it when they require it.
This is my first time using unpivot tables and creating functions. Open to suggestions on changing my dynamic unpivot query to best suits my needs.
Thanks in advance

Answer 1

In SQL Server you are not allowed to have dynamic SQL in functions.
You can create an SP that will return a record set generated using your code above.
UPDATE:
For the sake of completeness:
You can also call the above SP using (OPENQUERY) which would allow you to join to other tables without having to save to a temp table first but IMO it is an ugly way do this.
END UPDATE:
Another way is to create a VIEW that would un-pivot this table and create an SP that would regenerate this view after the process that adds a new column is completed e.g.
CREATE TABLE F1BWK_PLM_CAPEX( Val INT, Yr_17 INT, Yr_18 INT )
INSERT INTO F1BWK_PLM_CAPEX
SELECT 1, 10, 12
CREATE VIEW F1BWK_PLM_CAPEX_UNPIVOTED
AS
SELECT *
FROM F1BWK_PLM_CAPEX AS U
UNPIVOT (
Val2 FOR Yr IN (Yr_17, Yr_18)
)
AS UnpivotTable;
CREATE PROCEDURE dbo.Create_F1BWK_PLM_CAPEX_UNPIVOTED
AS
SET NOCOUNT ON
DECLARE #query as NVARCHAR(max);
DECLARE #cols as NVARCHAR(250) =
STUFF((
SELECT distinct ',' + QUOTENAME( Column_Name )
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'F1BWK_PLM_CAPEX'
AND COLUMN_NAME like 'YR_%'
For XML Path(''), type)
.value('.','NVARCHAR(MAX)' )
,1,1,'');
SELECT #query = '
ALTER VIEW F1BWK_PLM_CAPEX_UNPIVOTED
AS
SELECT *
FROM F1BWK_PLM_CAPEX AS U
UNPIVOT (
Val2 FOR Yr IN ( ' + #cols + ' )
)
AS UnpivotTable
';
EXEC(#query);
RETURN;
Now your query would become this:
SELECT *
FROM F1BWK_PLM_CAPEX_UNPIVOTED AS U
INNER JOIN [dbo].[F1_SYPAR_CTL] AS CTL
ON CTL.value = U.WS_VERS and CTL.PARAM_NAME = 'MBRC_CURR_PLM_BUDVER'
INNER JOIN [dbo].[F1_SYPAR_CTL] AS CTL2
ON CTL2.value = U.WS_NAME AND CTL2.PARAM_NAME = 'MBRC_CURR_PLM_BUDWSH'
At the end of the year a process runs that adds a new column:
ALTER TABLE F1BWK_PLM_CAPEX
ADD Yr_19 INT NOT NULL DEFAULT( 10 )
This process needs to run this SP to regenerate the view:
EXEC Create_F1BWK_PLM_CAPEX_UNPIVOTED
Notes:
I have replaced LIKE with = as your query matches on a full value. Only use LIKE when you need to specify wild cards.
I have also fixed a syntax error by changing Val to Val2 in the UNPIVOT query