I am trying to get the column position of a value while doing an unpivot on the columns col2, col3, col4 in SQL server

```
df1
col1     col2     col3     col4     
1        AAA      BBB
2        ABC      CCC      DDD

result
col1     [All]     [position]
1        AAA        1
1        BBB        2
2        ABC        1
2        CCC        2
2        DDD        3

```

I am able to unpivot the table by using the following

```
SELECT a.col1, a.[all]
from df1 as t
UNPIVOT
(
[all] for col_nm in (
    col2, col3, col4
) as a

```