module Sequel::SQL::QualifyingMethods

def qualify(qualifier)

:column.qualify(:table).qualify(:schema) # "schema"."table"."column"
:table.qualify(:schema) # "schema"."table"
:column.qualify(:table) # "table"."column"

Qualify the receiver with the given +qualifier+ (table for column/schema for table). 
def qualify(qualifier)
  QualifiedIdentifier.new(qualifier, self)
end