Google sheet query smarter way to get multiple criteria

I use a spreadsheet where I want a list of items which contains multiple criteria. (I need all cells in a range which contains the letter ‘a – g’

The formula I use now is

=query(Planning!G5:G37;  "select * where G contains 'a' or G contains 'b' or G contains 'c'   or ............  " ) 

What I want is the query get the criteria out of a list or an array, but I couldn’t figure out how to do this.