Adding `ref` and `raw` method to Database
Ref
The ref returns an instance of ReferenceBuilder, which can be used to mark string like values as database identifiers. For example:
Database.query().where('id', Database.ref('some-subquery.user_id'))With ref, the value will be considered as string literal. But we want it to be reference to a column from a sub query select
Raw
The raw is like rawQuery method, but you cannot execute it.