#notes# database chapter 5

not clear enough:

1.haven't mastered definition of :

　　a.tuple relational calculus

　　b.domain relational calculus

　　c.datalog

&& can't use these methods to solve pros smoothly

2.spent much time in understanding recursive programs && semantics of program.

3.still not get the meaning of 'implicatoin' (=>)

4.want to make practice in MS Access for deep understanding (G)QBE.

5.Recursion in Datalog...

 

@#.It's very effective && also terse to use Datalog, but unfortunately it's not widely used now.