数据库(关系数据库理论)

Q9X SC(SNo, CNo, Grade) , SNo è, SNo Student 'è, SC ' SNO è.
By Wei-gang Chen
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67(Logically implied)
6.11: |ê6 F, ,kê69X ±v F 67. =ù69X±d F, v@ ínSu&. - Armstrong's ún (Axioms): Armstrong' z, 1974c ' . d F ¤7'ê6'N F 'R. PF
By Wei-gang Chen
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e Y X U, u X → Y F ¤7. - dg¤& 'ê6', g'A^ 6u F
By Wei-gang Chen
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ê6ín5u: y2
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e X → Y, Z U, u XZ → YZ F ¤7. - X: SNo → SDept, dy P &
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AT¨iA9X(êATA9X)? z9XATdAáS|¤? - X A- ê , ¨ iX e 9 X n?
SCA(Sno, Sname, Sage, Sdept, CNo, Cname, Cpno, Credit, Course)
By Wei-gang Chen
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'Xê#OQX(pitfalls), #OAXeK:
F
~:
1 2
{SNo, CNo}
SC 9X'è; SNo Student 9 X' è
By Wei-gang Chen
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A:
éu9X, eèu, ?è. áS: Q?è'áS áS: Q?è'áS è: 9X R < U, F >, áS| U è, u è(All-key). ápp.174
By Wei-gang Chen
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e X → YZ, u X → Y, X → Z y¤á - X: SNo → {SDept, SName}, d)&:
SNo → Sdept, SNo → SName
By Wei-gang Chen
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ê6únX
O F ~f
1 2
;E'8E(Repetition of Information). Uv^rsv'8E.
By Wei-gang Chen
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có
~:
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PI'8E±9±r'8E, Lending(I, I¤Q, I]#, r, ±ár, ±ê) - , 'ê ~ (instance)
By Wei-gang Chen
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By Wei-gang Chen
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ê6únX: á584
: áS8R(Closure of attribute sets)
1
2
áS8 X 'RP X . # F |ê68, áS8 X U, e F kê 6 X → A, u A X - =: X = {A | X → A U d F Amstrong ún Xí }
ê6: AVg
Vg 3: ê6
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e X → Y, Y ê6u X, u Y ê 6u X. - ê 6 's P: X Y. → - ~f : (SNo, Sname) Sdept →
P P
By Wei-gang Chen
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ê6: AVg
Vg 4: D4ê6
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e X → Y, Y → Z, Y → X ¤á, u Z DRê 6u X. - ~f : SNo → SDept, SDept → DeptRoom, u DeptRomm D R 6u SNo DeptRoom vXú
1 6 'Xên
By Wei-gang Chen May 15, 2009
By Wei-gang Chen
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ùSN):
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có ê6 ê6è únX áS8'R è') uCX n
By Wei-gang Chen
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Q1, ò'X¤ 5 | R(U, D, dom, F), )'5#O' U F. éNK, k±eA6#OKs :
By Wei-gang Chen
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ê6únX: á584
OáS8R~f
1
R U, F , U = (A, B, C , G , H, I ), F = {A → B, A → C , CG → H, CG → I , B → H}
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2
O(AG )
+
(AG )+ = AG (AG )+ = ABCG , since A → B and A → C , then result = result ∪ B,... (AG )+ = ABCGH, since CG → H, then result = result ∪ H (AG )+ = ABCGHI , since CG → I , then result = r
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ê6: AVg
Vg 2: ê6
F
e X → Y, é X '?f8 X', k Y ê 6u X', u Y ê6u X. - ê 6 's P: X Y. → - ~f : (SNo, CNo) Grade →
F
By Wei-gang Chen
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ê6ín5u: 5u
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e X → Y, X → Z, u X → YZ ¤á
By Wei-gang Chen
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ê6ín5u: D4
-
e X → Y, WY → Z, u XW → Z ¤á - X CNo → CName, {CName, SNo} → Grade, u {CNo, Sno} → Grade ¤á
{SNo, SName} → {SDept, SName}
By Wei-gang Chen
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ê6ín5u: D4
-
e X → Y, and Y → Z, u X → Z F ¤7 - X: SNo → SDept, SDept → DeptRoom, DeptRoom Xú
By Wei-gang Chen
è'~f.
By Wei-gang Chen
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ê6è: è
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1 2
è~f:
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9X R 'áSáS| A, R 'è, A ,9X R 'è, u R ' A R ì R 'è. R ì9 X(Referencing relation); R &ì9X;
1 1 2 1 1 2 1 2
By Wei-gang Chen
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ê6(functional dependencies)
ê6
-
# R(U) áS8 U '9X, X U, Y U. eé R(U) '?U'9X r, UQü |Q X 'áS1, Q Y 'áS1, u X ê( Y, Y ê6u X. - P: X → Y X " "
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-
R<U, F>, U = (A, B, C, G, H, I ), F = {A → B, A → C, CG → H, CG → I, B → H }
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Some members of F+
1 2
A → H,
3 4
^DR A → B and B → H AG → I, ^y P , d A → C & AG → CG, , ^DR& AG → I CG → HI, ^ S u, CG → H CG → I .
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F
R(the closure of F)
.
By Wei-gang Chen
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ê6únX
ê6ín5u(#'X R(U, F))
1 2 3 4 5 6
g(Reexivity rule) yP(Augmentation rule) DR(Transitivity rule) Su(union rule) DR(Pseudotransitivity rule) )(Decomposition rule)
By Wei-gang Chen
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ê6(functional dependencies)
ê6{ü~f
éu9X, A → B ¤á - éu9X, B → A U¤á
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By Wei-gang Chen
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ê6(functional dependencies)
ê6,~f:
1 2 3
k9X: Student (Sno, SName, Sdept, Ssex, Birthdate), ±4kXe'ê69X¤á:
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Lending
1
2 3
4
,Ikm±ár, uTI'branch-name, branch-city, assets8 E Emg , XDowntown; ;m'L¤; 5g&ED. Xé Downtown I']#'c U; s^ null : Xt,Ivk±?r, u s^ null . Qê^ null é'(J.