create temp table msl09(c1 text, c2 text);
insert into msl09 values ('123', '321');
insert into msl09 values ('abcd', '321');
insert into msl09 values ('abcdw', '321');
insert into msl09 values('234', '4a66');
insert into msl09 values('234', '466');

create or replace function test() returns integer as $$
delete from msl09 where c2 = (select c2 from msl09 where c1 = '123');
delete from msl09 where c1 = (select c2 from msl09);
select 1;
$$ language sql;

select test();
select * from msl09;