如何将Mysql查询转换为关系代数？

Question

如何编写mysql查询 关系代数中的SELECT book, COUNT(book) FROM booking GROUP BY book;？ 我认为Gcount(book)(booking)但似乎不对。

我遵循Arun K Majumdar和Pritimoy Bhattacharya的数据库管理系统标准。提前谢谢。

Answer 1

将您的SQL命令修改为： select booking.book,count(booking.book) as book_count from booking GROUP BY booking.book

等效关系代数命令：

π booking.book, book_count γ booking.book; COUNT(booking.book)→book_count booking

来源：http://dbis-uibk.github.io/relax/calc.htm

我希望这有帮助！