1. Distributed Database Management System
Lecture 05

2. Virtual University of Pakistan
Data Model
A set of tools/ constructs used to model a database
Record/Semantic
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3. Virtual University of Pakistan
Legacy Data Models
Hierarchical
Network
Relational
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4. Virtual University of Pakistan
Relational Data Model
Two major Strengths
Three Components
Relational databases based on relational Data Model
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5. Virtual University of Pakistan
A relation R defined over domains D1, D2, …., Dn is a set of n-tuples, <d1, d2, …, dn> such that <d1 D1……, dnDn
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6. Virtual University of Pakistan
Schemes in RDB
EMP(eNo, eName, eTitle, eSal, pNo, eResp, pDur)
PROJ(pNo, pName, bud)
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7. Virtual University of Pakistan
Each of the attribute in these two relations has a domain, like…
Domains need not to be distinct
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8. Keys

9. Virtual University of Pakistan
Primary Key
Minimum nonempty subset of a relation whose values uniquely identify each tuple in relation
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10. Virtual University of Pakistan
The superset of the key is super key, like…
We also have candidate, alternate, secondary, foreign
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11. Table

12. Virtual University of Pakistan
Relation represented in a two dimensional form
eDur
eResp
pNo
eSal
eTitle
eName
eNo
EMP
pBud
pName
pNo
PROJ
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13. Virtual University of Pakistan
eDur
eResp
pNo
eSal
eTitle
eName
eNo
E01
E03
E05
E06
E07
E08
Naeem
Rahila
Narjis
Aslam
Hafeez
Liaqat
Supr
Desin
Prog
Eng
Anlyst
500
700
850
900 P1 P2 P3
Work
Mangr
Cons 12 7 15 10
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14. Virtual University of Pakistan
After defining a relation’s scheme, it is populated
Tuples are rows and attributes are cols
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15. Virtual University of Pakistan
Attributes get values from same domain
Can have NULL value, but….
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16. Virtual University of Pakistan
Normalization
Step-by-step reversible process to produce anomalies free smarter tables
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17. Virtual University of Pakistan
Anomalies Types….
Major step is decomposition
Universal Relation approach
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18. Virtual University of Pakistan
Three Normal Forms
BCNF
Lossless decomposition
Dependency preservation
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19. Virtual University of Pakistan
Dependency Structure
Norm. based on dependencies
Up to BCNF on FDs
MVD and P-JD
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20. Virtual University of Pakistan
Dependencies
A relation R defined on attributes A(A1, A2, …., An), if XA, YA, if for each value of X
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21. Virtual University of Pakistan
there is a unique value in Y, then X functionally determines Y, X Y
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22. Virtual University of Pakistan
If X Y and there is a ZX and ZY, then X partially determines Y or Y is partially dependent on X
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23. Virtual University of Pakistan
A relation R defined on attributes A(A1, A2, …., An), if XA, YA, ZA, if for each value of X, there is
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24. Virtual University of Pakistan
there is unique value of (Y,Z) pair and Z depends only on X then X multidetermines Z, X Z
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25. Virtual University of Pakistan
P-J Dependency
A relation R defined on attributes A(A1, A2, …., An), if XA, YA, ZA, if R is equal to join of X, Y and Z then (X, Y, Z) constitute project-join dependency for R
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26. Virtual University of Pakistan
1NF, attributes have only atomic values
2NF, there are no partial dependencies
3NF, for each XY where Y is not in X, either X is a superkey of R or Y is prime attribute
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