3-1








1Object


3MessageEncapsulation


2(Primary Key)


3.2
R
S
3.3
σ=’’ AND =1987()


R
S=
R(X,Y)S(Y,Z), X,Y,ZRSRXRXxYxSY
R
S
A
B
C
D
A1
B1
C1
D1
A1
B1
C2
D2
A1
B1
C3
D3
A2
B2
C1
D1
A2
B2
C2
D2
A3
B2
C1
D1
A3
B2
C1
D2
C
D
E
C1
D1
D1
C2
D2
D2
A
B
A1
B1
A1
B1
2.

3.




R(U)URXYU R “XY”“YX”
2.

1.

3.
XY YFull Functional DependencyX YPartial Function DependencyX
4.
→→

→ →→

2


3.10 S()2NF
2NF
S2()
S3()
S1 S2 S32NF
2S12()

RRBC
ZAddBC
}
{