这就像在Python中更新字典一样。如果记录不存在，则创建它，否则更新它。

cur.execute('SELECT COUNT(*) FROM persons WHERE id=?;', (id,))
if cur.fetchone()[0] == 0:
    # Record does not exist.
    cur.execute('INSERT INTO persons (id, username, points, score) VALUES (?,?,?,?);', (id,username,points,score)
else:
    # Record exists.
    cur.execute('UPDATE persons SET points=points+?, score=score+? WHERE id=?;', (points,score,id))

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自版本3.24.0起，SQLite支持UPSERT：

sql = """
  INSERT INTO persons (id, username, points, score) VALUES (?, ?, ?, ?)
  ON CONFLICT(id) DO UPDATE
  SET points = points + EXCLUDED.points,
      score = score + EXCLUDED.score;
"""
cur.execute(sql, (id, username, points, score))

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假设id是唯一的，这将起作用。
参见demo。