欢迎补充 [mysql跨表查询](https://github.com/minibear2333/interview-leetcode/blob/master/interview/mysql.md#%E6%80%8E%E4%B9%88%E8%B7%A8%E8%A1%A8%E6%9F%A5%E8%AF%A2%E8%BF%98%E6%9C%89%E6%8E%92%E5%BA%8F%E5%92%8C%E7%BF%BB%E9%A1%B5%E6%80%8E%E4%B9%88%E5%81%9A%E7%9A%84)
