Compare two value in Oracle Procedure - oracle

Question

i'm very noob at that, can you help me? I have to see if cash>=price and cash is taken from "portafoglio" from "studente" table and price is taken from "costo" from "corso" table but it gave me several error
CREATE OR REPLACE FUNCTION PAGA_CORSO
(
MAT IN NUMBER
, COR IN NUMBER
, DAT IN DATE
, cash DOUBLE PRECISION
, price DOUBLE PRECISION
) RETURN BOOLEAN AS
BEGIN
SELECT portafoglio
INTO cash
FROM studente
WHERE matricola=MAT;
SELECT costo
INTO price
FROM corso
WHERE codicecorso=COR;
IF cash >= price THEN
RETURN FALSE;
ELSE
RETURN TRUE;
END IF;
END PAGA_CORSO;
Thanks!

Answer 1

You are missing OUT clauses, because you want to return values "out" of the function,
SQL> CREATE OR REPLACE FUNCTION PAGA_CORSO
2 (
3 MAT IN NUMBER
4 , COR IN NUMBER
5 , DAT IN DATE
6 , cash DOUBLE PRECISION
7 , price DOUBLE PRECISION
8 ) RETURN BOOLEAN AS
9 BEGIN
10 SELECT sal
11 INTO cash
12 FROM emp
13 WHERE empno=MAT;
14
15 SELECT deptno
16 INTO price
17 FROM dept
18 WHERE deptno=COR;
19
20 IF cash >= price THEN
21 RETURN FALSE;
22 ELSE
23 RETURN TRUE;
24 END IF;
25 END PAGA_CORSO;
26 /
Warning: Function created with compilation errors.
SQL>
SQL> sho err
Errors for FUNCTION PAGA_CORSO:
LINE/COL ERROR
-------- -----------------------------------------------------------------
10/5 PL/SQL: SQL Statement ignored
11/10 PLS-00403: expression 'CASH' cannot be used as an INTO-target of
a SELECT/FETCH statement
12/5 PL/SQL: ORA-00904: : invalid identifier
15/5 PL/SQL: SQL Statement ignored
16/10 PLS-00403: expression 'PRICE' cannot be used as an INTO-target of
a SELECT/FETCH statement
17/5 PL/SQL: ORA-00904: : invalid identifier
Now we add OUT to the definition
SQL> CREATE OR REPLACE FUNCTION PAGA_CORSO
2 (
3 MAT IN NUMBER
4 , COR IN NUMBER
5 , DAT IN DATE
6 , cash out DOUBLE PRECISION
7 , price out DOUBLE PRECISION
8 ) RETURN BOOLEAN AS
9 BEGIN
10 SELECT sal
11 INTO cash
12 FROM emp
13 WHERE empno=MAT;
14
15 SELECT deptno
16 INTO price
17 FROM dept
18 WHERE deptno=COR;
19
20 IF cash >= price THEN
21 RETURN FALSE;
22 ELSE
23 RETURN TRUE;
24 END IF;
25 END PAGA_CORSO;
26 /
Function created.
Also, "double precision" is rare - I'd suggest you probably just want to go with NUMBER.