Transposing a table in SQL server

Question

I am using SQL Server 2005 for my application. I have a table in my stored procedure which has two columns, C1 and C2. I want to transpose this table such that the values of

Answer 1

This is probably a case where dynamic sql is your friend. Assuming your base table's name is "Transpose":

--Get a Unique List of values from C1 --> These will be our column headers
DECLARE @Unique TABLE (C1 VARCHAR(25), fUsed BIT DEFAULT 0);
INSERT INTO @Unique (C1) SELECT DISTINCT C1 FROM Transpose;

DECLARE @TransSQL NVARCHAR(4000);
DECLARE @ColID NVARCHAR(25);

SET @TransSQL = N'SELECT ' 

--Loop over unique C1 values and construct the select statement
SELECT @ColID = (SELECT TOP 1 C1 FROM @Unique WHERE fUSed = 0);
WHILE @@ROWCOUNT <> 0 AND @ColID IS NOT NULL
BEGIN
    SET @TransSQL = @TransSQL + 'CASE C1 WHEN ' + '''' + @ColID + '''' + ' THEN C2 ELSE NULL END AS ' + @ColID + ', '

    --Update flag in table so we don't use this field again
    UPDATE u SET fUsed = 1 FROM @Unique u WHERE C1 = @ColID;
    SELECT @ColID = (SELECT TOP 1 C1 FROM @Unique WHERE fUSed = 0);
END

--Remove Trailing comma and add FROM clause
DECLARE @SQL NVARCHAR(4000)
SET @SQL = LEFT(@TransSQL,LEN(@TransSQL) -1) + ' FROM Transpose'

--For debugging purposes
PRINT @SQL;

--Execute the dynamic sql
EXEC sp_executesql @SQL;

This won't achieve the exact layout your question described because their isn't a key field to group the results by. Instead, the output will look like the following:

M1     M2      M3
U1     NULL    NULL
U2     NULL    NULL
U3     NULL    NULL
NULL   U4      NULL
NULL   U5      NULL
NULL   NULL    U6

If your base table has a key field the query can be modified slightly to group the results by the key field and probably come a bit closer to your stated goal for the resulting data.