Thanks a million for your response.

What I really mean is that I don't have the column identifier. It is only there to see what I need. How can I get it in SQL?

I have a huge table with 10m entries. But there is only 500,000 different. The only way to identify each different entry is concatenating many columns. The final result is a 20 characters long, which is not very useful for calculations. I would prefer a number.

Can I create a variable stored in a column that increases every time there is a change in some of the other columns? Is there a way to simplify the 20-characters-long variable?...