Power Query folder combine -- file combining -- faster?

peterhui50 can you not use this:

=List.ContainsAny({"A".."Z"}, Text.ToList([Column1]))

It returns true or false. It is case sensitive. So the "xxxxx" value returns false since it isn't in A-Z

Changing it to this returns Yes or No.

if List.ContainsAny({"A".."Z"}, Text.ToList([Column1])) then "Yes" else "No"

And changing it to this is case insensitive.

if List.ContainsAny({"A".."Z", "a".."z"}, Text.ToList([Column1])) then "Yes" else "No"

peterhui50 - post back with performance enhancements. I don't know how much more efficient a List.Contains with Text.ToList is vs a single if/then/else with Text.Contains, but it surely must be more efficient than 26 of them!

Thanks to mahoneypat for asking the right question. I was just thinking originally of a lot of data. Looking at the transformations should have been at the top of my list as well.