用关系代数表达一下句子:
比如:
问题如下:
Student(sid: integer, name: string, age: integer, gender: string, gpa: real)
Course(cid:interger, cname: string, teacher: string)
Enroll(sid: integer, cid:integer, grade: integer)
用关系代数表达一下句子:
比如:
问题如下:
Student(sid: integer, name: string, age: integer, gender: string, gpa: real)
Course(cid:interger, cname: string, teacher: string)
Enroll(sid: integer, cid:integer, grade: integer)