我想在Postgresql數據庫的sql中添加此函數

Question

我寫了這個功能：

create function check_same_price() returns integer as $result$
declare
 result integer;
begin
 set res = (select *
  from (select count(distinct title), price_dvd_buy
  from dvd_to_buy
  group by price_dvd_buy) as dummy
  where count>1);
if (res==none) then result=0;
else result=1;
end if;
end;
$result$ language plpgsql;

如果同一標題的價格相同，則該函數返回0，否則返回1。執行此檢查的原因是我希望同一部電影的價格相同； 我正在使用phppgadmin進行管理。 我收到此錯誤：

SQL error:

ERROR:  error of sintax to or near "("
LINE 5:  set res = (select *

怎么了，我不知道要解決。 謝謝！

Answer 1

create function check_same_price()
returns boolean as $$
begin
   return exists(select count(distinct title)
                    from dvd_to_buy
                   group by price_dvd_buy
                   having count(distinct title) > 1)
end;
$$ language plpgsql;