SQL Server 2005 - Dynamic PIVOT query - sql

Question

I require your kind help on a PIVOT query problem.
The scenario is I have a voting system. Comprises of 3 tables.
Elections, Candidates, Votes.
The PIVOT relates to PIVOTing the Candidate names as Columns and having the VOTE data as the data.
So far I have attemped this and not got it to work, I've gotten into a muddle with it :(
CREATE TABLE #MYELECTIONS (E_POSITION_CODE INT, E_POSITIONNAME VARCHAR(50))
INSERT INTO #MYELECTIONS VALUES (147,'MANAGER')
INSERT INTO #MYELECTIONS VALUES (148,'CHEF')
INSERT INTO #MYELECTIONS VALUES (149,'WAITER')
CREATE TABLE #MYCANDIDATES (C_CANDIDATE_CODE INT,
C_CANDIDATENAME VARCHAR (50), C_POSITION_CODE INT)
INSERT INTO #MYCANDIDATES VALUES (100,'TOM CRUISE', 147)
INSERT INTO #MYCANDIDATES VALUES (101,'MICKY MOUSE', 147)
INSERT INTO #MYCANDIDATES VALUES (103,'DONALD DUCK', 147)
INSERT INTO #MYCANDIDATES VALUES (100,'TOM CRUISE', 148)
CREATE TABLE #MYVOTES (V_POSITION_CODE INT,
V_CANDIDATE_CODE INT, VOTINGPREFERENCE SMALLINT)
INSERT INTO #MYVOTES VALUES (147,100,1)
INSERT INTO #MYVOTES VALUES (147,100,1)
INSERT INTO #MYVOTES VALUES (147,100,1)
INSERT INTO #MYVOTES VALUES (147,100,1)
INSERT INTO #MYVOTES VALUES (147,101,1)
INSERT INTO #MYVOTES VALUES (147,101,1)
INSERT INTO #MYVOTES VALUES (147,103,1)
INSERT INTO #MYVOTES VALUES (148,100,1)
INSERT INTO #MYVOTES VALUES (148,100,1)
DECLARE #DynamicPivotQuery AS NVARCHAR(MAX)
DECLARE #ColumnName AS NVARCHAR(MAX)
DECLARE #MyPositionCode AS INT
SET #MyPositionCode = 147
DECLARE #MyOutput AS NVARCHAR(MAX)
--Get distinct values of the PIVOT Column
SELECT #ColumnName = ISNULL(#ColumnName + ',','')
+ QUOTENAME(C_CANDIDATENAME)
FROM (SELECT TOP 100 PERCENT C_CANDIDATENAME
FROM #MYCANDIDATES
WHERE C_POSITION_CODE = #MyPositionCode
ORDER BY C_CANDIDATE_CODE) AS C_CANDIDATENAME
--Prepare the `PIVOT` query using the dynamic sql
SET #DynamicPivotQuery =
N'SELECT ROW_NUMBER() OVER (ORDER BY E_POSITIONNAME) AS Idnum,
E_POSITIONNAME AS [Position Name], ' + #ColumnName + '
FROM #MYVOTES
INNER JOIN #MYELECTIONS
ON (#MYVOTES.V_POSITION_CODE = #MYELECTIONS.E_POSITION_CODE)
PIVOT(SUM(VOTINGPREFERENCE))
FOR C_CANDIDATENAME IN (' + #ColumnName + ') AS PVTTable
WHERE #MYELECTIONS.E_POSITION_CODE = 147'
--Execute the Dynamic Pivot Query
EXEC sp_executesql #DynamicPivotQuery,
#MyOutput = #MyOutput OUTPUT
SELECT #MyOutput
DROP TABLE #MYELECTIONS
DROP TABLE #MYCANDIDATES
DROP TABLE #MYVOTES
It has to be a dynamic PIVOT as the Candidate Names that I want to Pivot as Columns, could be dynamic depending on how many Candidates there are for an Election position.
The desired output for the above would be like this:-
Election #MyPositionCode = 147
Idnum Position_Name TOM CRUISE MICKY MOUSE DONALD DUCK...
1 MANAGER 4 2 1
Election #MyPositionCode = 148
Idnum Position_Name TOM CRUISE MICKY MOUSE DONALD DUCK...
1 CHEF 2 0 0

Answer 1

Try this
DECLARE #MyPositionCode AS INT
SET #MyPositionCode = 147
Declare the variables for selecting dynamic columns
DECLARE #DynamicPivotQuery AS NVARCHAR(MAX)
DECLARE #ColumnName AS NVARCHAR(MAX)
DECLARE #cols NVARCHAR (MAX)
SELECT #cols = COALESCE (#cols + ',[' + C_CANDIDATENAME + ']', '[' + C_CANDIDATENAME + ']')
FROM
(
SELECT TOP 100 PERCENT C_CANDIDATENAME
FROM #MYCANDIDATES
WHERE C_POSITION_CODE = #MyPositionCode
ORDER BY C_CANDIDATE_CODE
) PV
ORDER BY C_CANDIDATENAME desc
If you want to replace NULL with zero
DECLARE #NulltoZeroCols NVARCHAR (MAX)
SELECT #NullToZeroCols = SUBSTRING((SELECT ',ISNULL(['+C_CANDIDATENAME+'],0) AS ['+C_CANDIDATENAME+']'
FROM
(
SELECT TOP 100 PERCENT C_CANDIDATENAME
FROM #MYCANDIDATES
WHERE C_POSITION_CODE = #MyPositionCode
ORDER BY C_CANDIDATE_CODE
)TAB
ORDER BY C_CANDIDATENAME desc FOR XML PATH('')),2,8000)
Now pivot it dynamically. I have written the logic inside
DECLARE #query NVARCHAR(MAX)
SET #query = '-- You can apply ROW_NUMBER() here which is the data after pivot
SELECT ROW_NUMBER() OVER (ORDER BY E_POSITIONNAME) AS Idnum,
,E_POSITIONNAME,'+#NullToZeroCols+'
FROM
(
-- Select data before pivot
SELECT TOP 100 PERCENT ME.E_POSITIONNAME,MC.C_CANDIDATENAME,
COUNT(MC.C_CANDIDATENAME) OVER(PARTITION BY ME.E_POSITIONNAME,MC.C_CANDIDATENAME) CNT
FROM #MYELECTIONS ME
JOIN #MYCANDIDATES MC ON ME.E_POSITION_CODE=MC.C_POSITION_CODE
JOIN #MYVOTES MV ON MC.C_CANDIDATE_CODE=MV.V_CANDIDATE_CODE
AND MV.V_POSITION_CODE=MC.C_POSITION_CODE
WHERE MC.C_POSITION_CODE = ' + CAST(#MyPositionCode AS VARCHAR(30)) + '
) x
PIVOT
(
MIN(CNT)
FOR C_CANDIDATENAME IN (' + #cols + ')
) p
;'
EXEC SP_EXECUTESQL #query
Click the below link. If the result is not auto-generated, press RUN QUERY button.
Click here to view result