CREATE OR REPLACE FUNCTION public.do_something(
    mon date,
    some_id character varying)
  RETURNS void AS
$BODY$
declare
	sql_query text;
begin
        delete from some_table 
        using another table
	where some_table.id = another_table.id 
                 and same_month(do_something.mon, another_table.some_date::date);

	select sql_query = format('
	insert into some_table (id, some_value)
        select  another_table.id, %s
        from    another_table
        where  some_id = %L
                  and same_month(%L, another_table.some_date::date);', formula, do_something.some_id, do_something.mon)
        from    rules_table
        where  rule_table.some_id = do_something.some_id
        limit 1;

	execute(sql_query);

	return ;
end
$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;

DO $$
BEGIN
	PERFORM do_something('2017-08-01'::date, '123123123');
END$$ LANGUAGE plpgsql;

select format('
	insert into a3f_reward (
		aid,
		reward
	)
	select  "TransID", 
                %s
        from    a3f
        where   "PartAIN" = %L
                and same_month(%L, a3f."ConfirmDate"::date);', formula, ain, mon)
	from	a3f_reward_rules
	where	a3f_reward_rules.ain = part_ain
	limit 1 into sql_query;