Question

I’ve just started to get into SQL Server deeper and I have a problem. I have to transform a row into a column, but I can’t figure it out.

The row looks like this:

   Columns:      T1 T2 T3 .........T20
    Values:      1   0  9 ......... 15

I want to receive something like this:

    Col  Val
    ________
    T1    1
    T2    0
    T3    9
    ........
    T20   15

I know i have to use a pivot, i have read about this, but can’t figure it out

Answer 1

You have to use UNPIVOT table operator for this, like this:

SELECT col, val
FROM Tablename AS t
UNPIVOT
(
   Val
   FOR Col IN (T1, T2, ..., T20)
) AS u;

SQL Fiddle Demo.

---

Update 1

If you want to do this dynamically for any number of columns, without the need to write them manually, the only way I can think of is by reading these columns from the table information_schema.columns to get the list of columns’ names of the table. Then use dynamic SQL to compose the statement FOR col IN ... dynamically like this:

DECLARE @cols AS NVARCHAR(MAX);
DECLARE @query AS NVARCHAR(MAX);

select @cols = STUFF((SELECT distinct ',' +
                        QUOTENAME(column_name)
                      FROM information_schema.columns
                      WHERE table_name = 'tablename'
                      FOR XML PATH(''), TYPE
                     ).value('.', 'NVARCHAR(MAX)') 
                        , 1, 1, '');

SELECT @query = ' SELECT col, val
                  FROM tablename AS t
                  UNPIVOT
                  (
                  val
                  FOR col IN ( ' + @cols + ' )
                  ) AS u;';

EXECUTE(@query);

Updated SQL Fiddle Demo

This will give you:

| COL | VAL |
-------------
|  T1 |   1 |
| T10 |  15 |
| T11 |  33 |
| T12 |  31 |
| T13 |  12 |
| T14 |  10 |
| T15 |  12 |
| T16 |   9 |
| T17 |  10 |
| T18 |   2 |
| T19 |  40 |
|  T2 |   0 |
| T20 |  21 |
|  T3 |   9 |
|  T4 |   2 |
|  T5 |   3 |
|  T6 |  10 |
|  T7 |  14 |
|  T8 |  15 |
|  T9 |  20 |