具有自动增量字段的复合主键

Question

我使用sqlite3并且我有以下表格，我想知道是否有可能实现下面描述的结果作为想要的行为。我不确定这会有多大用处，但似乎将来可能会有用。

我有以下表格：

topics:
  topic_id int primary key,
  topic_name str,
  topic_author str,

posts:
  tid int,
  pid integer primary key autoincrement,
  post_author str,
  post str,
  FOREIGN KEY(tid) REFERENCES topics(topic_id)

当我插入表格帖子时：

  15, null, "Author1", "Post1"
  15, null, "Author1", "Post2"
  16, null, "Author1", "Post1"
  16, null, "Author1", "Post1"

我明白了：

  15, 1, "Author1", "Post1"
  15, 2, "Author1", "Post2"
  16, 3, "Author1", "Post1"
  16, 4, "Author1", "Post1"

而不是我想要的：

  15, 1, "Author1", "Post1"
  15, 2, "Author1", "Post2"
  16, 1, "Author1", "Post1"
  16, 2, "Author1", "Post1"

这可能吗？