SQL Function

CREATE OR REPLACE FUNCTION get_square(n INT)
RETURNS INT AS $$
DECLARE
  result INT;
BEGIN
  result := n * n;
  RETURN result;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION add_numbers(a INT, b INT)
RETURNS INT AS $$
BEGIN
  RETURN a + b;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION check_age(age INT)
RETURNS TEXT AS $$
BEGIN
  IF age >= 18 THEN
    RETURN 'Adult';
  ELSE
    RETURN 'Minor';
  END IF;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION get_user_name(uid INT)
RETURNS TEXT AS $$
DECLARE
  returneddd_name TEXT;
BEGIN
  SELECT name INTO returneddd_name -- name will be injected to returneddd_name
  FROM users
  WHERE id = uid;

  RETURN returneddd_name;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION add_numbers(a INT, b INT)
RETURNS INT AS $$
BEGIN
  RETURN a + b;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION check_age(age INT)
RETURNS TEXT AS $$
BEGIN
  IF age >= 18 THEN
    RETURN 'Adult';
  ELSE
    RETURN 'Minor';
  END IF;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION get_user_name(uid INT)
RETURNS TEXT AS $$
DECLARE
  returneddd_name TEXT;
BEGIN
  SELECT name INTO returneddd_name -- name will be injected to returneddd_name
  FROM users
  WHERE id = uid;

  RETURN returneddd_name;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION get_all_users()
RETURNS TABLE(id INT, name TEXT) AS $$
BEGIN
  RETURN QUERY
  SELECT id, name FROM users;
END;
$$ LANGUAGE plpgsql;