Question

I’m using PL/SQL, and I would like to check if a record exists in a table, I’ve tried using when exists or if not exists, but I end up with exception.

Select name from nameTable where name = nameFromArgument;

When the procedures starts, and I put in a wrong name, which is not in the database I’m getting an error, can’t even handle it

I’ve tried something like this:

PL/SQL check if query returns empty

edit:

sorry, the select I’ve put before was just an example, the whole code [ sorry for names of variables… ] is here:

CREATE OR REPLACE
PROCEDURE SELLSTOCKS
( IloscAkcji IN NUMBER
, NazwaAkcji IN VARCHAR2
, IdRachunkuMaklerskiego IN NUMBER
)  AS
Bledna_ilosc EXCEPTION;
Bledna_nazwa EXCEPTION;
amount NUMBER;
stocksCash number;
idRachunku number;
stocksOnDealerSide number;
temp number;
tempus akcje_uzytkownika.nazwa % type;
BEGIN

--Select nazwa into tempus from akcje_uzytkownika where nazwa = nazwaakcji;
--dbms_output.put_line(tempus);

  dbms_output.put_line('pre');
 select nazwa into tempus from akcje_uzytkownika where nazwa = nazwaakcji;
 dbms_output.put_line('pre2');
 if tempus!=null then
    if ( iloscakcji> amount) THEN
  raise Bledna_ilosc;
  else
  select ilosc, cena_sztuki into amount, stockscash from akcje_uzytkownika where nazwa= NazwaAkcji and id_rachunku_maklerskiego= IdRachunkuMaklerskiego;
 dbms_output.put_line(amount);
 dbms_output.put_line(stockscash);
  amount :=amount - iloscakcji;
  dbms_output.put_line(amount);
  update akcje_uzytkownika set ilosc= amount  where nazwa=NazwaAkcji and  id_rachunku_maklerskiego= idrachunkumaklerskiego;
  stockscash:= iloscAkcji * stocksCash;
  dbms_output.put_line(stockscash);
  select id_rachunku into idrachunku from rachunek_maklerski where id_rachunku_maklerskiego= idrachunkumaklerskiego; 
  temp:=SALDOUPDATE(stockscash, idrachunku);
  select ilosc into stocksOnDealerSide from akcje where nazwa = nazwaAkcji;
  stocksOnDealerSide := stocksondealerside+ iloscakcji;
  dbms_output.put_line(stocksOnDealerSide);
  update akcje set ilosc = stocksondealerside where nazwa = nazwaAkcji;
  end if;
  else
  dbms_output.put_line('post');
  end if;
EXCEPTION

  when Bledna_ilosc then
  dbms_output.put_line('Bledna ilosc');
  when Bledna_nazwa then
  dbms_output.put_line('Bledna nazwa');

END SELLSTOCKS;

I’m using oracle sql developer 1.5.5

BEGIN

--Select nazwa into tempus from akcje_uzytkownika where nazwa = nazwaakcji;
--dbms_output.put_line(tempus);

  dbms_output.put_line('pre');
  select nazwa into tempus from akcje_uzytkownika where nazwa = nazwaakcji;
  dbms_output.put_line('pre2');
  exception when no_data_found then
  raise no_data_found;

-- is this the right place?

  select ilosc, cena_sztuki into amount, stockscash from akcje_uzytkownika where nazwa= NazwaAkcji and id_rachunku_maklerskiego= IdRachunkuMaklerskiego;
  dbms_output.put_line(amount);
  dbms_output.put_line(stockscash);
  amount :=amount - iloscakcji;
  dbms_output.put_line(amount);
  if ( iloscakcji> amount) THEN
  raise Bledna_ilosc;
  else
  update akcje_uzytkownika set ilosc= amount  where nazwa=NazwaAkcji and  id_rachunku_maklerskiego= idrachunkumaklerskiego;
  stockscash:= iloscAkcji * stocksCash;
  dbms_output.put_line(stockscash);
  select id_rachunku into idrachunku from rachunek_maklerski where id_rachunku_maklerskiego= idrachunkumaklerskiego; 
  temp:=SALDOUPDATE(stockscash, idrachunku);

……..

Answer 1

You have four main things that are wrong (that I can see).

Firstly, tempus!=null will never work. As null is the absence of information you can’t use the (in)equality operator when checking for nulls. Non-existence != non-existence. The correct syntax is to use is null, or in your case tempus is not null.

Secondly, if ( iloscakcji> amount) THEN will never evaluate to true as you don’t initialise the value amount. A number cannot be greater than null as it doesn’t exist. You have to initialise the variable amount. Maybe you meant the next select statement to be above this?

Thirdly, all of your select ... into ... statements are into single variables – not user defined table-types. This means that if 0 rows are returned by your query a no_data_found exception will be raised. If more than one row is returned a too_many_rows exception will be raised.

If you’re only expecting at most one row then you don’t need to worry too much about too_many_rows. This should really be enforced by a unique constraint on your table if possible. For example I would expect that nazwa should be unique on akcje_uzytkownika.

no_data_found is slightly different and is, I expect, what you meant to by tempus != null. Assuming that amount has been initialised to a value this can be re-written as:

begin

    -- do some stuff    
    begin

       select nazwa into tempus from akcje_uzytkownika where nazwa = nazwaakcji;

    -- If there-s no data catch the exception.
    exception when no_data_found then
       if ( iloscakcji > amount) then
          raise Bledna_ilosc;
       end if;

    end;        
    -- do some more stuff

end;

Lastly, and it’s not really a mistake but, your code is fairly unreadable. I would consider using a lot more whitespace so that you can see what’s going on.

P.S. By Oracle version I meant 11gr2 or 10g etc but it doesn’t make any difference in this case.