How to fix Ambiguous parameter in PostgreSQL

-- WRONG: Ambiguous
SELECT id, name FROM users JOIN orders ON id = id;

-- RIGHT: Qualified
SELECT u.id, u.name FROM users u JOIN orders o ON u.id = o.user_id;

-- WRONG: Same $1 used as both text and integer
CREATE FUNCTION check_value(param VARCHAR) AS $$
BEGIN
  IF param = 5 THEN  -- Comparing text to integer
    ...
  END IF;
END;
$$;

-- RIGHT: Explicit cast
CREATE FUNCTION check_value(param VARCHAR) AS $$
BEGIN
  IF param::INTEGER = 5 THEN
    ...
  END IF;
END;
$$;

-- WRONG: Ambiguous - which "name" do we mean?
CREATE FUNCTION update_user(id INTEGER, name VARCHAR) AS $$
BEGIN
  UPDATE users SET name = name WHERE user_id = id;
END;
$$;

-- RIGHT: Qualified with function name
CREATE FUNCTION update_user(id INTEGER, name VARCHAR) AS $$
BEGIN
  UPDATE users SET name = update_user.name WHERE user_id = update_user.id;
END;
$$;

CREATE FUNCTION process_data() AS $$
<<outer_block>> DECLARE
  name VARCHAR;
BEGIN
  <<inner_block>> DECLARE
    name VARCHAR;
  BEGIN
    -- Refer explicitly
    INSERT INTO log (msg) VALUES (outer_block.name || ' vs ' || inner_block.name);
  END;
END;
$$;

CREATE FUNCTION update_user(id INTEGER, name VARCHAR) AS $$
#variable_conflict use_variable
BEGIN
  UPDATE users SET name = name WHERE user_id = id;
END;
$$ LANGUAGE plpgsql;

-- Avoid shadowing columns
CREATE FUNCTION update_user(p_id INTEGER, p_name VARCHAR) AS $$
BEGIN
  UPDATE users SET name = p_name WHERE user_id = p_id;
END;
$$;