In SQL (SQL Server) I would use: Col LIKE '[A-L]%'
to find all Col values starting with letter A through to L.
How do you do this in Looker, I’ve tried putting [A-L]% in matches (advanced).
There’s no built-in functionality that would let you do that at the moment.
Greg_sanders had a workaround using parameter and templated filters here:
https://community.looker.com/explores-36/how-to-use-regex-filter-on-string-fields-10353