Is it allowed to write a SQL function in Oracle to return more than data types?

Question

I am trying to understand about SQL functions in Oracle, I was wondering if it is possible to write a SQL function which can return a Number or a Varchar2 based on the conditions in the program.

Answer 1

You can SORT OF do that using a return type of ANYDATA. But the calling query or PL/SQL block would have to use a CASE statement to evaluate the return type in order to do anything with it. Very simple demonstration below.

    CREATE OR REPLACE FUNCTION AnyData_Test
      (
       p_Value_In            IN      VARCHAR2
      )
      RETURN AnyData
AS
      ad_Test_Var            ANYDATA;
BEGIN
      CASE
            WHEN p_Value_In = 'Varchar2' THEN ad_Test_Var := SYS.ANYDATA.ConvertVarchar2('VC2');
            WHEN p_Value_In = 'Number'   THEN ad_Test_Var := SYS.ANYDATA.ConvertNumber(123);
            ELSE                              ad_Test_Var := SYS.ANYDATA.ConvertDate(SYSDATE);
      END CASE;
      RETURN ad_Test_Var;
END AnyData_Test;
/

SELECT
      AnyData.GetTypeName(AnyData_Test('Varchar2'))    AS Return_Type_V
     ,AnyData.AccessVarchar2(AnyData_Test('Varchar2')) AS Return_Type_V_Value
     --
     ,AnyData.GetTypeName(AnyData_Test('Number'))      AS Return_Type_N
     ,AnyData.GetTypeName(AnyData_Test('Nope'))        AS Return_Type_D
FROM dual
;
      
SELECT
      CASE AnyData.GetTypeName(AnyData_Test('Varchar2'))
            WHEN 'SYS.VARCHAR2' THEN AnyData.AccessVarchar2(AnyData_Test('Varchar2'))
            ELSE 'Other'
      END AS Quick_Test
FROM dual;

Answer 2

Oracle functions can be as complex as you want, and you can apply as much logic as you want. A very basic example of a function with logic inside

• The function only admits two parameters, one as varchar and other as number
• C2 can only be A or B. Other value is an error
• The function based on that returns a number which is the sum of c1 +10 if it is A, +100 if it is B.

Let's make it work

SQL> create or replace function my_example ( c1 in number , c2 in varchar2 ) return 
number
is
        begin
        if c2 = 'A'
        then
           return c1 + 10 ;
        elsif c2 = 'B'
        then
  2    3    4    5    6    7    8    9             return c1 + 100 ;
        else
           raise_application_error ( -20001, 'c1 only allows A or B' );
 10   11   12   end if;
end;
 13   14  /

Function created.

SQL> select my_example( 1 , 'A' ) from dual ;

MY_EXAMPLE(1,'A')
-----------------
               11

SQL>  select my_example( 1 , 'B' ) from dual ;

MY_EXAMPLE(1,'B')
-----------------
              101

SQL>

UPDATE

If you want to return either numbers of strings, use return varchar2

SQL> create or replace function my_example ( c1 in number , c2 in varchar2 ) return varchar2
  2  is
  3     begin
        if c2 = 'A'
        then
           return c1 + 10 ;
  4    5    6    7      elsif c2 = 'B'
  8     then
  9        return c1 + 100 ;
 10     elsif c2= 'C'
        then
                return 'Alfa' ;
 11   12   13   else
           raise_application_error ( -20001, 'c1 only allows A or B' );
        end if;
end;
/ 14   15   16   17

Function created.

SQL> select my_example( 1 , 'C' ) from dual ;

MY_EXAMPLE(1,'C')
--------------------------------------------------------------------------------
Alfa

SQL> select my_example( 1 , 'A' ) from dual ;

MY_EXAMPLE(1,'A')
--------------------------------------------------------------------------------
11

SQL>  select my_example( 1 , 'B' ) from dual ;

MY_EXAMPLE(1,'B')
--------------------------------------------------------------------------------
101

Then you can also apply ( 12.2 onwards ) the VALIDATE_CONVERSION standard function to determine whether the return of the original function is a string or a number

SQL> select validate_conversion ( my_example( 1 , 'B' ) as number ) from dual ;

VALIDATE_CONVERSION(MY_EXAMPLE(1,'B')ASNUMBER)
----------------------------------------------
                                             1

SQL> select validate_conversion ( my_example( 1 , 'C' ) as number ) from dual ;

VALIDATE_CONVERSION(MY_EXAMPLE(1,'C')ASNUMBER)
----------------------------------------------
                                             0

SQL>

1 means true number, 0 means it is not a number