Transpose Row to Column in SQL Server 2000 - sql

Question

I am trying to convert rows into columns in SQL Server 2000. Although all rows converted into required columns but i unable to get the value converted into the respective columns.
My code is:
DROP TABLE prePivot1
DROP TABLE results1
CREATE TABLE prePivot1 (
[StudentId] uniqueidentifier
, [Sub_Abbr] Varchar(100)
, [Total_marks] MONEY
)
CREATE TABLE results1 (
[StudentId] uniqueidentifier
)
INSERT INTO prePivot1
SELECT '{4FD7CBBA-1621-4102-B4A3-000BF92E2F6E}', 'ENG', 55
UNION SELECT '{4FD7CBBA-1621-4102-B4A3-000BF92E2F6E}', 'MBEN', 90
UNION SELECT '{4FD7CBBA-1621-4102-B4A3-000BF92E2F6E}', 'ECO', 80
UNION SELECT '{4FD7CBBA-1621-4102-B4A3-000BF92E2F6E}', 'PSc', 45
UNION SELECT '{4FD7CBBA-1621-4102-B4A3-000BF92E2F6E}', 'PSY', 23
UNION SELECT '{AD288712-5C97-446B-8AFE-003FC845B56B}', 'ENG', 90
UNION SELECT '{AD288712-5C97-446B-8AFE-003FC845B56B}', 'ECO', 44
UNION SELECT '{AD288712-5C97-446B-8AFE-003FC845B56B}', 'PSc', 45
UNION SELECT '{AD288712-5C97-446B-8AFE-003FC845B56B}', 'BST', 23
UNION SELECT '{AD288712-5C97-446B-8AFE-003FC845B56B}', 'ASS', 80
UNION SELECT '{AD288712-5C97-446B-8AFE-003FC845B56B}', 'PSY', 93
DECLARE #sql VARCHAR(8000)
DECLARE #pivot varchar(10)
DECLARE pivotCursor CURSOR LOCAL READ_ONLY FOR
SELECT DISTINCT
[Sub_abbr]
FROM
prePivot1
OPEN pivotCursor
FETCH NEXT FROM pivotCursor INTO #pivot
WHILE (##FETCH_STATUS = 0) BEGIN
SET #sql = '
ALTER TABLE results1 ADD [' + CAST(#pivot AS VARCHAR(10)) + '] INT'
EXEC (#sql)
FETCH NEXT FROM pivotCursor INTO #pivot
END
CLOSE pivotCursor
INSERT INTO results1 ([studentId])
SELECT DISTINCT [StudentId] FROM prePivot1
OPEN pivotCursor
FETCH NEXT FROM pivotCursor INTO #pivot
WHILE (##FETCH_STATUS = 0) BEGIN
SET #sql = '
UPDATE results1
SET
[' + CAST(#pivot AS VARCHAR(10)) + '] = pp.[total_marks]
FROM
prePivot1 pp
WHERE
pp.[total_marks] = ' + CAST(#pivot AS VARCHAR(10)) + '
AND pp.[studentId] = results1.[studentId]'
EXEC (#sql)
FETCH NEXT FROM pivotCursor INTO #pivot
END
CLOSE pivotCursor
DEALLOCATE pivotCursor
SELECT * FROM results1
Please help me how do i do to get the expected result.
Thanking you in advance.

Answer 1

There are a couple of things wrong with your predicate here:
pp.[total_marks] = ' + CAST(#pivot AS VARCHAR(10)) + '
You are filtering on the wrong column
You are not generating a proper string with the #pivot part.
This is what it looks like when you print out your dynamic sql string. Notice that it causes a join on prePivot1.total_marks column to results1.ECO column which is not what you're intending.
UPDATE
results1
SET
[ECO] = pp.[total_marks]
FROM
prePivot1 AS pp
WHERE
pp.[total_marks] = ECO
AND pp.[studentId] = results1.[studentId]
Corrected version (you also don't need to cast the variable):
pp.[Sub_Abbr] = ''' + #pivot + '''
A slightly less error prone solution would be to parameterize your dynamic sql:
-- Change #sql --> nvarchar(4000)
SET #sql = N'
UPDATE
results1
SET
' + QUOTENAME(#pivot) + N' = pp.[total_marks]
FROM
prePivot1 AS pp
WHERE
pp.[Sub_Abbr] = #Sub_Abbr
AND pp.[studentId] = results1.[studentId];';
EXEC sp_executesql
#stmt = #sql,
#params = N'#Sub_Abbr varchar(10)',
#Sub_Abbr = #pivot;
This is the general pattern I've used in sql2k to pivot just for reference:
(I'm assuming here that StudentId, Sub_Abbr is unique though the schema doesn't explicitly confirm this)
SELECT
[StudentId],
MAX(CASE WHEN [Sub_Abbr] = 'ASS' THEN [Total_marks] ELSE NULL END) AS [ASS],
MAX(CASE WHEN [Sub_Abbr] = 'BST' THEN [Total_marks] ELSE NULL END) AS [BST],
MAX(CASE WHEN [Sub_Abbr] = 'ECO' THEN [Total_marks] ELSE NULL END) AS [ECO],
MAX(CASE WHEN [Sub_Abbr] = 'ENG' THEN [Total_marks] ELSE NULL END) AS [ENG],
MAX(CASE WHEN [Sub_Abbr] = 'MBEN' THEN [Total_marks] ELSE NULL END) AS [MBEN],
MAX(CASE WHEN [Sub_Abbr] = 'PSc' THEN [Total_marks] ELSE NULL END) AS [PSc],
MAX(CASE WHEN [Sub_Abbr] = 'PSY' THEN [Total_marks] ELSE NULL END) AS [PSY]
FROM
[dbo].[prePivot1]
GROUP BY
[StudentId];