# into the column clause of an enclosing select, and should instead
# act like a single scalar column
+ # allow corresponding_column to return None
# indicates if this select statement, as a subquery, should automatically correlate
# its FROM clause to that of an enclosing select, update, or delete statement.
# note that the "correlate" method can be used to explicitly add a value to be correlated.
self.__wherecorrelator = Select._CorrelatedVisitor(self, True)
self.__fromvisitor = Select._FromVisitor(self)
self.order_by_clause = self.group_by_clause = None