Want to add a null value to the first row column and create a new column

[PNC97]

I had the rows like this 

The highlighted need to be my output.

Thanks for help

[MattBSlalom · Accepted solution]

This question is a little vague.  You could simply Union a null() row with your source "Merged" column to get the highlighted result... but I think you're wanting to use the Index fields to lookup the "Merged" value from the row that matches the 2nd index field.  If that's the case, you need a Join tool plus a Union tool to capture the output from the different anchors to carry forward the unmatched / null value.

Sample workflow below & attached.

[PNC97]

You Saved my Day 🙂