ERROR: input parameters after one with a default value must also have defaults in Postgres

Question

I am trying to set default value to a variable within the function in parameter list but getting an error:

ERROR: input parameters after one with a default value must also have defaults

Example:

 Create or replace function test(name varchar default null
                               , city varchar default null
                               , phonenumber varchar(20) default null
                               , out sno bigint, address varchar)
   returns void as
 $$
 Declare 
        phonenumber AS VarChar(20);
 Begin
        phonenumber : =phonenumber; 

    SELECT sno = MAX(ssno)+1 FROM emp;

    IF(sno IS NULL)  then
           sno=IDENT_CURRENT('emp')+1;
    end;

    raise info '%',name;
    raise info '%',city;
    raise info '%',phonenumber;
    raise info '%',address;

    insert into emp(ename,ecity,ephonenumber,eaddress)
    values(name,city,phonenumber,address);

 end;
 $$
 langauge plpgsql;

Answer 1

Much is not right in your example. Or rather: not much is right in your example.

CREATE OR REPLACE FUNCTION f_test(
     name text = NULL
   , city text = NULL
   , phonenumber text = NULL
    ,address text = NULL
   , OUT sno bigint)
RETURNS void AS
 $func$
DECLARE 
    phonenumber AS VarChar(20);  -- would collide with parameter name
BEGIN
phonenumber := phonenumber;      -- nonsense

SELECT INTO sno  max(ssno) + 1 FROM emp;  -- SELECT INTO for assignment

IF sno IS NULL THEN
  sno := ident_current('emp') + 1;
END IF;

RAISE NOTICE '%, %, %, %', name, city, phonenumber, address;

INSERT INTO emp(ename, ecity, ephonenumber, eaddress)
VALUES (name, city, phonenumber, address);

END
$func$  LANGUAGE plpgsql;

Major points

• The error message speaks for itself:

  input parameters after one with a default value must also have defaults.

  That's almost what the manual has on that:

  All input parameters following a parameter with a default value must have default values as well.

• It wouldn't make sense to combine RETURNS void with OUT parameters.

• Don't declare variable names colliding with parameter names. Completely useless here.

• The plpgsql assignment operator is :=, not =.

• You don't normally use the RAISE level INFO. You want NOTICE instead.

• SELECT without target is not possible in plpgsql, you want SELECT INTO.

• IF is terminated with END IF not with END.

Simplify further

Use COALESCE to replace your IF statement. Aggregate functions return a row even if the table is empty.
But you don't need that either. Just use the RETURNING clause to return the new id directly:

CREATE OR REPLACE FUNCTION f_test(
     name text = NULL
   , city text = NULL
   , phonenumber text = NULL
   , address text = NULL
   , OUT sno bigint)
AS
$func$
BEGIN
RAISE NOTICE '%, %, %, %', name, city, phonenumber, address;

INSERT INTO emp(ename, ecity, ephonenumber, eaddress)
VALUES (name, city, phonenumber, address)
RETURNING ssno
INTO   sno;             -- Assuming you want to return autoincremented id 

END
$func$  LANGUAGE plpgsql;

Answer 2

Try

Create or replace function test(
out sno bigint, 
address varchar,
name varchar default null, 
city varchar default null, 
phonenumber varchar(20) default null)
   returns void as ..