SQL Server 2005 - column names based on variable passed in pivot query - sql-server

Question

I have following query which takes 2 parameters.
YearNumber
MonthNumber
In my pivot query, I am trying to select columns based on #Year_Rtl variable. I need to select data for the year passed, last year and last last year. Since the data being displayed on UI is table format divided by #Year_Rtl, I decided to write a pivot query for that as below.
In the query, it works fine if I hard code [#Year_Rtl], [#Year_Rtl - 1], [#Year_Rtl - 2] to [2012], [2011], [2010]. But since the year passed can be anything, I want columns to be named dynamically.
DECLARE #Month_Rtl int
DECLARE #Year_Rtl int
SET #Year_Rtl = 2012
SET #Month_Rtl = 1
SELECT
'Data 1', [#Year_Rtl], [#Year_Rtl - 1], [#Year_Rtl - 2]
FROM
(SELECT [Yr_No], Qty
FROM dbo.Table1 t
WHERE (t.Col1 = 10) AND
(t.Col2 = '673') AND
((t.Mth_No = #Month_Rtl AND t.Yr_No = #Year_Rtl) OR
(t.Mth_No = 12 AND t.Yr_No IN (#Year_Rtl - 1, #Year_Rtl - 2)))
) p PIVOT (SUM(Qty)
FOR [Yr_No] IN ([#Year_Rtl], [#Year_Rtl-1], [#Year_Rtl-2])
) AS pvt
Above query throws following errors:
Error converting data type nvarchar to smallint.
The incorrect value "#Year_Rtl" is supplied in the PIVOT operator.
Invalid column name '#Year_Rtl - 1'.
Invalid column name '#Year_Rtl - 2'.

Answer 1

Since you can use dynamic SQL, I'd go with a macro-replacement approach. You're identifying areas of the query that must be dynamically replaced with placeholders (e.g. $$Year_Rtl) and then calculating their replacement values below. I find that it keeps the SQL statement easy to follow.
DECLARE #SQL NVarChar(2000);
SELECT #SQL = N'
SELECT
''Data 1'', [$$Year_Rtl], [$$Year_RtlM1], [$$Year_RtlM2]
FROM
(SELECT [Yr_No], Qty
FROM dbo.Table1 t
WHERE (t.Col1 = 10) AND
(t.Col2 = ''673'') AND
((t.Mth_No = $$Month_Rtl AND t.Yr_No = $$Year_Rtl) OR
(t.Mth_No = 12 AND t.Yr_No IN ($$Year_RtlM1, $$Year_RtlM2)))
) p PIVOT (SUM(Qty)
FOR [Yr_No] IN ([$$Year_Rtl], [$$Year_RtlM1], [$$Year_RtlM2])
) AS pvt';
SELECT #SQL = REPLACE(#SQL, '$$Year_RtlM2', #Year_Rtl - 2);
SELECT #SQL = REPLACE(#SQL, '$$Year_RtlM1', #Year_Rtl - 1);
SELECT #SQL = REPLACE(#SQL, '$$Year_Rtl', #Year_Rtl);
SELECT #SQL = REPLACE(#SQL, '$$Month_Rtl', #Month_Rtl);
PRINT #SQL;
-- Uncomment the next line to allow the built query to execute...
--EXECUTE sp_ExecuteSQL #SQL;

Answer 2

Since consuming code will also have to be flaky under this scheme (e.g. selecting columns based on "position" rather than name) - why not normalize the columns by performing a DATEDIFF(year,Yr_No,#Year_Rtl), and work from there? Those columns will always be 0, -1 and -2...

Answer 3

You need to look into Dynamic SQL Pivoting.
I recommend reading Itzik Ben-Gan's T-SQL Fundamentals where he goes over how to do this.
Alternatively try this article if you don't want to buy the book.

Answer 4

Maybe this will help:
First getting the columns with a tally function like this:
DECLARE #Month_Rtl int,
#Year_Rtl int,
#Year_Rtl_Start INT,
#cols VARCHAR(MAX),
#values VARCHAR(MAX)
SET #Year_Rtl = 2012
SET #Month_Rtl = 1
SET #Year_Rtl_Start=2009
;WITH Years ( n ) AS (
SELECT #Year_Rtl_Start UNION ALL
SELECT 1 + n FROM Years WHERE n < #Year_Rtl )
SELECT
#cols = COALESCE(#cols + ','+QUOTENAME(n),
QUOTENAME(n)),
#values = COALESCE(#values + ','+CAST(n AS VARCHAR(100)),
CAST(n AS VARCHAR(100)))
FROM
Years
ORDER BY n DESC
The variable #cols contains the columns that is in the pivot and the variable #values contains the years for the IN. The #Year_Rtl is the end year and the #Year_Rtl_Start is the start for you range.
Then declaring and executing the dynamic pivot like this:
DECLARE #query NVARCHAR(4000)=
N'SELECT
''Data 1'', '+#cols+'
FROM
(
SELECT
[Yr_No], Qty
FROM
dbo.Table1 t
WHERE
t.Col1 = 10
AND t.Col2 = ''673''
AND
(
(
t.Mth_No = '+CAST(#Month_Rtl AS VARCHAR(10))+'
AND t.Yr_No = '+CAST(#Year_Rtl AS VARCHAR(10))+'
)
OR
(
t.Mth_No = 12
AND t.Yr_No IN ('+#values+'))
)
) p
PIVOT
(
SUM(Qty)
FOR [Yr_No] IN ('+#cols+')
) AS pvt'
EXECUTE(#query)