PLSQL - Function - Increment an Integer

PLSQL - Function - Increment an Integer.sql

-- Solution 1
CREATE OR REPLACE FUNCTION increment(i integer) RETURNS integer as $$
  BEGIN
    return i + 1;
  END;
$$ LANGUAGE plpgsql;

-- Soluution 2
CREATE FUNCTION increment(i integer) RETURNS integer
AS 'select $1 + 1;'
LANGUAGE sql;

-- Solution 3
CREATE FUNCTION increment (IN age integer, OUT integer) 
AS 'SELECT age + 1'
LANGUAGE SQL;

-- Solution 4
CREATE FUNCTION increment(@age INT) {
returns INT as
Begin
  return @age + 1;
end;