Phan6
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Transcript of Phan6
- 1. Never stop improving quality www.elarion.com
2. Mc ch chn ha CSDL
- Biu din c mi quan h trong CSDL
3. Trnh sai st khi thm, xa, sa d liu 4. Trnh phi xy dng li cu trc ca cc quan h khi cn n cc kiu d liu mi 5. Gii thiu
- Cc dng chun : C 4 dng chun c bn.
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- Dng chun1 (1 Normal Form - 1NF)
- 6. Dng chun 2 (2 Normal Form - 2NF
7. Dng chun 3 (3 Normal Form - 3NF) 8. Dng chun Boyce-Codd 9. Dng chun 1(1/3)
- nh ngha:
-
- Mt lc quan h Q c gi l t chun 1 nu mi thuc tnh ca Q u lthuc tnh n .
- 10. Mt lc CSDL c gi l t chun 1 nu mi lc quan h con Qi ca n u t dng chun 1.
11. Thuc tnh n :
-
-
- Gi s c lc quan h Q.
- 12. Mt thuc tnh A c gi l thuc tnh nnu n khng phi l s tch hp ca nhiu thuc tnh khc.
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13. Dng chun 1(2/3)
- V d:
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- Ta c quan h sau :
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- Phan_Cong( MaNV , MaPhong)
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- MaPhong khng l thuc tnh n.
- 14. Quan h Phan_Cong khng t chun 1.
15. Cch khc phc :
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- Phan_Cong( MaNV, MaPhong )
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16. Dng chun 1 (3/3)
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- Quan h Phan_Cong t chun 1.
17. Dng chun 2(1/3)
- nh ngha :
-
- Mt lc quan h Q c gi l t chun 2 nu :
-
-
- Q t chun 1
- 18. Mi thuc tnh khng kha ca Q iu ph thuc y vo cc kha ca Q.
-
- Mt lc CSDL c gi l t chun 2 nu mi lc con Qi ca n u t chun 2.
19. Dng chun 2(2/3)
- V d : Ta c quan h Q sau :
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- NhanVien_DuAn ( MaNV, MaDA, TenNV, TenDA, DiaDiemDA, SoGio). Vi cc ph thuc hm:
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- F1: MaNV, MaDU SoGio
- 20. F2: MaNV TenNV
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- 21. F3: MaDA TenDA, DiaDiemDA.
- Lc quan h Q ny cha t chun 2 v :
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- MaDA TenDA, DiaDiemDA cha t chun 2
- 22. MaNV TenNV cha t chun 2.
23. Dng chun 2(3/3)
- Cch khc phc : Tch lc quan h Q ny thnh cc lc quan h sau :
-
- Q1 ( MaNV ,TenNV)
- 24. Q2 ( MaDA , TenDA, DiaDiemDA)
25. Q3 ( MaDA,MaNV ,SoGio)
- Lc quan h Q t chun 2.
26. Nhn xt:
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- Nu lc quan h Q ch c 1 kha K v K ch c mt thuc tnh th Q t dng chun 2
- 27. Mt lc d quan h Q chun 2 vn c th cha ng s trng lp thng tin
28. Dng chun 3(1/3)
- nh ngha :
-
- Mt lc quan h Q c gi l t chun 3 nu:
-
-
- Q t chun 2
- 29. Mi thuc tnh khng kha ca Q u khng ph thuc bc cu vo mt kha no ca Q.
-
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- Mt lc CSDL c gi l t chun 3 nu mi lc con Qi ca n u t chun 3.
30. Dng chun 3(2/3)
- V d : Xt lc quan h sau :
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- NhanVien_DonVi ( MaNV , HoTen, NgaySinh, DiaChi, MADV, TenDV, DiaDiemDV). Vi cc ph thuc hm:
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- F1 : MaNV HoTen, NgaySinh, DiaChi, MaDV, TenDV, DiaDiemDV.
- 31. F2: MaDVTenDV, DiaDiemDV.
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- Q cha t chun 3 v cc thuc tnh TenDV, DiaDiemDV ph thuc bc cu vo kha chnh.
32. Dng chun 3(3/3)
- Cch khc phc : Tch lc Q thnh cc lc con sau :
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- Q1 ( MaNV , HoTen, NgaySinh, DiaChi, MaDV).
- 33. Q2 ( MADV , TenDV, DiaDiemDV).
- Q t chun 3
34. Nhn xt:
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- Chnh ph thuc hm bc cu l nguyn nhn dn n tnh trng trng lp thng tin.
- 35. Dng chun 3 ltiu chun ti thiutrong thit k c s d liu.
36. Dng chun Boyce-Codd (BCNF)(1/2)
- L dng chun c tnh n tt c cc kha ng vin nn c nhiu rng buc hn dng chun 3
37. BCNF - Mt quan h dng chun BCNF nu vch nu mi phn t quyt nh ca cc ph thuchm (nm bn trimi tn) l cc kha ng vin. 38. Nhn xt:
-
- Nu 1 l c quan h Qtdng chun BC thcngtdng chun 3 .
- 39. Trong 1 l c quan h Qtdng chun BC, vic kim tra ph thuc hm ch yu lkim tra kha ni.
40. Dng chun Boyce-Codd (BCNF)(2/2)
- V d:
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- T_HNG (SH , NgyH, MKH )
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- F1 = { SHNgyH, MKH }
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- CHITIT_H ( SH, MHH , SL ng )
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- F2 = { SH, MHHSL ng }
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- 2 quan h u t dng chun Boyce-Codd.
41. Phng php phn r(1/10)
- Qu trnh chun ha 1 l c CSDL:
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- Nhm mc ch nng cao cht l ng thit k
- 42. a cc l c quan h con t dng chun thp ln dng chun cao h n m ti thiu phi l dng chun 3.
- Ph ng php phn r l 1 ph ng php dng chun ha 1 l c CSDL
43.
- Vic chun ha 1 l c quan h hay 1 l c CSDL phi bo m yu cu: bo ton thng tin
44. Php phn r Q thnh Q 1 , Q 2 , c gi l bo ton thng tin nu:
- T Q : T Q= T Q[Q1] |>