CREATE TABLE Employee
(
EmpId INT,
salary int,
commission_pct int
);

INSERT INTO Employee VALUES(1,10000,10);
INSERT INTO Employee VALUES(2,20000,15);

CREATE OR REPLACE FUNCTION GET_ANNUAL_INCOME (iEmpId IN INT) 
RETURN FLOAT 
IS annual_income FLOAT;
BEGIN  
  SELECT salary *12 +(commission_pct*salary*12) 
  INTO annual_income
  FROM Employee 
  WHERE EmpId = iEmpId;
  
  RETURN(annual_income);
END;

SCOTT@orcl> SELECT banner FROM v$version
  2  /

BANNER
--------------------------------------------------------------------------------
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
PL/SQL Release 12.1.0.2.0 - Production
CORE	12.1.0.2.0	Production
TNS for 64-bit Windows: Version 12.1.0.2.0 - Production
NLSRTL Version 12.1.0.2.0 - Production

5 rows selected.

SCOTT@orcl> CREATE TABLE Employee
  2  (
  3  EmpId INT,
  4  salary int,
  5  commission_pct int
  6  );

Table created.

SCOTT@orcl> 
SCOTT@orcl> INSERT INTO Employee VALUES(1,10000,10);

1 row created.

SCOTT@orcl> INSERT INTO Employee VALUES(2,20000,15);

1 row created.

SCOTT@orcl> 
SCOTT@orcl> CREATE OR REPLACE FUNCTION GET_ANNUAL_INCOME (iEmpId IN INT)
  2  RETURN FLOAT
  3  IS annual_income FLOAT;
  4  BEGIN
  5    SELECT salary *12 +(commission_pct*salary*12)
  6    INTO annual_income
  7    FROM Employee
  8    WHERE EmpId = iEmpId;
  9  
 10    RETURN(annual_income);
 11  END;
 12  /

Function created.

SCOTT@orcl> SHOW ERRORS
No errors.
SCOTT@orcl> SELECT employee.*,
  2  	    get_annual_income (EmpId) AS annual_income
  3  FROM   employee
  4  /

     EMPID     SALARY COMMISSION_PCT ANNUAL_INCOME
---------- ---------- -------------- -------------
         1      10000             10       1320000
         2      20000             15       3840000

2 rows selected.

CREATE OR REPLACE FUNCTION GET_ANNUAL_INCOME (iEmpId IN INT) 
RETURN FLOAT 
IS annual_income FLOAT;
BEGIN  
  SELECT salary *12 +(commission_pct*salary*12) 
  INTO annual_income
  FROM Employee 
  WHERE EmpId = iEmpId;
  
  RETURN annual_income;
exception
when no_data_found then
  return 0;
END;
/