Positional vs. Named Parameter Notation v11

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You can use either positional or named parameter notation when passing parameters to a function or procedure. If you specify parameters using positional notation, you must list the parameters in the order that they are declared; if you specify parameters with named notation, the order of the parameters is not significant.

To specify parameters using named notation, list the name of each parameter followed by an arrow (=>) and the parameter value. Named notation is more verbose, but makes your code easier to read and maintain.

A simple example that demonstrates using positional and named parameter notation follows:

CREATE OR REPLACE PROCEDURE emp_info (
    p_deptno        IN     NUMBER,
    p_empno         IN OUT NUMBER,
    p_ename         IN OUT VARCHAR2,
)
IS
BEGIN
    dbms_output.put_line('Department Number =' || p_deptno);
    dbms_output.put_line('Employee Number =' || p_empno);
    dbms_output.put_line('Employee Name =' || p_ename;
END;

To call the procedure using positional notation, pass the following:

emp_info(30, 7455, 'Clark');

To call the procedure using named notation, pass the following:

emp_info(p_ename =>'Clark', p_empno=>7455, p_deptno=>30);

Using named notation can alleviate the need to re-arrange a procedure’s parameter list if the parameter list changes, if the parameters are reordered or if a new optional parameter is added.

In a case where you have a default value for an argument and the argument is not a trailing argument, you must use named notation to call the procedure or function. The following case demonstrates a procedure with two, leading, default arguments.

CREATE OR REPLACE PROCEDURE check_balance (
    p_customerID  IN NUMBER DEFAULT NULL,
    p_balance     IN NUMBER DEFAULT NULL,
    p_amount      IN NUMBER
)
IS
DECLARE
    balance NUMBER;
BEGIN
   IF (p_balance IS NULL AND p_customerID IS NULL) THEN
      RAISE_APPLICATION_ERROR
          (-20010, 'Must provide balance or customer');
   ELSEIF (p_balance IS NOT NULL AND p_customerID IS NOT NULL) THEN
      RAISE_APPLICATION_ERROR
          (-20020,'Must provide balance or customer, not both');
   ELSEIF (p_balance IS NULL) THEN
      balance := getCustomerBalance(p_customerID);
   ELSE
      balance := p_balance;
   END IF;

   IF (amount > balance) THEN
      RAISE_APPLICATION_ERROR
        (-20030, 'Balance insufficient');
   END IF;
END;

You can only omit non-trailing argument values (when you call this procedure) by using named notation; when using positional notation, only trailing arguments are allowed to default. You can call this procedure with the following arguments:

check_balance(p_customerID => 10, p_amount = 500.00)

check_balance(p_balance => 1000.00, p_amount = 500.00)

You can use a combination of positional and named notation (mixed notation) to specify parameters. A simple example that demonstrates using mixed parameter notation follows:

CREATE OR REPLACE PROCEDURE emp_info (
    p_deptno        IN     NUMBER,
    p_empno         IN OUT NUMBER,
    p_ename         IN OUT VARCHAR2,
)
IS
BEGIN
    dbms_output.put_line('Department Number =' || p_deptno);
    dbms_output.put_line('Employee Number =' || p_empno);
    dbms_output.put_line('Employee Name =' || p_ename;
END;

You can call the procedure using mixed notation:

emp_info(30, p_ename =>'Clark', p_empno=>7455);

If you do use mixed notation, remember that named arguments cannot precede positional arguments.

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