Intersection of two relations

Question

Say I have two relations that hold records in the same model, such as:

@companies1 = Company.where(...)
@companies2 = Company.where(...)

Ho

Answer 1

I solve similar problem this way

Company.connection.unprepared_statement do
  Company.find_by_sql "#{@companies1.to_sql} INTERSECT #{@companies2.to_sql}"
end

We need unprepared_statement block here because latest Rails versions use prepared statements to speed up arel queries, but we need pure SQL in place.