并:
差:
笛卡儿积:
投影:
选择:
交:
联接:
除:
例题:
参考连接:
https://blog.csdn.net/qq_37521566/article/details/80854134
https://blog.csdn.net/qq_39368007/article/details/86586563
元组演算
例题:
参考连接:
https://blog.csdn.net/xqf309/article/details/8865269
参考连接:
https://blog.csdn.net/qq_37521566/article/details/80854134
https://blog.csdn.net/qq_39368007/article/details/86586563
参考连接:
https://blog.csdn.net/xqf309/article/details/8865269