CODEWITHSUNDEEP
sqlsql-serversql-server-2008
tlehman
tlehman

Reputation: 5167

SQL Pivoting from rows to columns leaves nothing but NULL values

I have a table variable, called @t, it is an instance of the specsAndModel type I defined here: 

CREATE TYPE specsAndModel AS TABLE
(
    specName VARCHAR(50)
    ,specVal VARCHAR(50)
)

Doing a select specName,specVal from @t gives data of the form:

specName              | specVal
--------------------------------
[modelNumber]         | F00-B4R
[Internal Switch(es)] | 2.00000
[Number of Ports]     | 1.00000
[Color Insulator]     | Yellow

I inserted the first row so that when I transpose the table, there will be a modelNumber field. I intend to join the transposed table to another on that field.

In order to account for a different number of records for different models, I constructed the pivot statement using string concatenation:

DECLARE @cols NVARCHAR(MAX);
DECLARE @query NVARCHAR(MAX);
SELECT @cols = COALESCE(@cols + ',' + specName, specName) FROM @t;

SET @query = N'SELECT ' + @cols 
+ N' FROM @var src' 
+ N' PIVOT (MAX(specVal) FOR specName in (' + @cols + N')) pvt;';

The query string looks like this: 

SELECT [modelNumber],[Internal Switch(es)],[Number of Ports],[Color Insulator] 
FROM @var src 
PIVOT 
(
  MAX(specVal) 
  FOR specName in ([modelNumber],[Internal Switch(es)],[Number of Ports],[Color Insulator])
) pvt;

Finally, I use sp_executesql to pass in the @t variable, then execute the @query string:

EXEC sp_executesql @query, N'@var specsAndModel readonly', @t

The result is this:

[modelNumber] | [Internal Switch(es)] | [Number of Ports] | [Color Insulator]
-----------------------------------------------------------------------------
NULL          | NULL                  | NULL              | NULL

I get the null values for all models, I constructed a toy example of this pivot here on sqlfiddle and it works as expected. I am not sure what I'm doing wrong.

How can I transpose this table without getting null values?

Upvotes: 0

Views: 974

Answers (1)

Taryn
Taryn

Reputation: 247650

A couple of things to fix:

First, remove the [ from around your specName values on your INSERT statement.

Second, change the way you get your columns to this. This will add the [ around the specName values:

DECLARE @cols NVARCHAR(MAX);
DECLARE @query NVARCHAR(MAX);
select @cols = STUFF((SELECT distinct ',' + QUOTENAME(specName) 
                    from @t
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

If you do that, then your script will work:

DECLARE @cols NVARCHAR(MAX);
DECLARE @query NVARCHAR(MAX);
select @cols = STUFF((SELECT distinct ',' + QUOTENAME(specName) 
                    from @t
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

SET @query = N'SELECT ' + @cols 
+ N' FROM @var src' 
+ N' PIVOT (MAX(specVal) FOR specName in (' + @cols + N')) pvt;';

EXEC sp_executesql @query, N'@var specsAndModel readonly', @t

See SQL Fiddle with Demo

Upvotes: 5

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