ORA-06502 in a stored procedure

Hello I have this simple procedure that compiles fine but after I initialize the variables the error is this.

The table is created like this

Create table vcelar_pomocky 
(
    cislo_nakupu Number(5,0) NOT NULL ,
    cislo_ula Number(5,0) NOT NULL ,
    rodne_cislo Varchar2 (30) NOT NULL ,
    datum_nakupu Date NOT NULL ,
    nazov Varchar2 (20) NOT NULL ,
    typ_polozky Varchar2 (20) NOT NULL ,
    cena_polozky Number(5,2) NOT NULL ,

    primary key (cislo_nakupu) 
) 
/

The procedure looks like this:

CREATE OR REPLACE PROCEDURE quera_pomocky
(
v_cislo_nakupu  IN  VCELAR_POMOCKY.cislo_nakupu%TYPE,
v_nazov         OUT VCELAR_POMOCKY.nazov%TYPE,
v_cena_polozky  OUT VCELAR_POMOCKY.cena_polozky%TYPE
)
IS
BEGIN
    SELECT  nazov || ' ' || typ_polozky,cena_polozky
        INTO v_nazov,v_cena_polozky
        FROM VCELAR_POMOCKY
        WHERE v_cislo_nakupu = cislo_nakupu AND rodne_cislo = '750927/3913';
END quera_pomocky;
/

VARIABLE p_nazov VARCHAR2(20);
VARIABLE p_cena_polozky VARCHAR2(20);
EXECUTE quera_pomocky(24, :p_nazov , :p_cena_polozky);
PRINT p_nazov p_cena_polozky;

And the error is

Error starting at line : 65 in command -
BEGIN quera_pomocky(24, :p_nazov , :p_cena_polozky); END;

Error report:

ORA-06502: PL/SQL: numeric or value error
ORA-06512: at "DOMA.QUERA_POMOCKY", line 9
ORA-06512: at line 1
06502. 00000 - "PL/SQL: numeric or value error%s"
*Cause: An arithmetic, numeric, string, conversion, or constraint error occurred. For example, this error occurs if an attempt is made to assign the value NULL to a variable declared NOT NULL, or if an attempt is made to assign an integer larger than 99 to a variable
declared NUMBER(2).

*Action: Change the data, how it is manipulated, or how it is declared so that values do not violate constraints.

Solution

You are putting this:

nazov || ' ' || typ_polozky

into a parameter

v_nazov OUT VCELAR_POMOCKY.nazov%TYPE

which is - in a table - declared as

nazov Varchar2 (20)

So: if length of nazov || ' ' || typ_polozky exceeds 20 characters (mind you: both are - in the table - declared as varchar2(20) which makes that concatenation's MAX length 41), you're in trouble.

I'd suggest you to set OUT parameter to e.g.

v_nazov OUT varchar2(50)