I have part of a query for a data dictionary in Oracle:
I am trying to change the value of the DATA_DEFAULT field in case it is null . When I make the query with the field that is commenting (blue arrow) I get the following result in the field DATA_DEFAULT :
But when I do it with the line indicated with the arrow in red I get the following error message referring to the variable that I highlight yellow, and if I put it in that place it is because in case it is not null I want you to give me back the same value:
In summary, what I want is that in the result of the query I do not get null in the field DATA_DEFAULT but an empty space (''). I tried to "cast" the variable after else without success, any suggestions are welcome.