Figure 14.1 Simplified version of the

Transcription

1 Figure. Simplified version of the COMPANY relational database schema. EMPLOYEE f.k. ENAME SSN BDATE ADDRESS DNUMBER DEPARTMENT f.k. DNAME DNUMBER DMGRSSN DEPT_LOCATIONS f.k. DNUMBER DLOCATION PROJECT f.k. PNAME PNUMBER PLOCATION DNUM WORKS_ON f.k. SSN f.k. PNUMBER HOURS Addison Wesley Longman, Inc. 000, Elmasri/Navathe, Fundamentals of Database Systems, Third Edition

2 Figure. Example relations for the schema of Figure.. EMPLOYEE ENAME SSN BDATE ADDRESS DNUMBER Zelaya,Alicia J. Wallace,Jennifer S. Narayan,Remesh K. Jabbar,Ahmad V. Borg,James E. DEPARTMENT DNAME DNUMBER DMGRSSN Administration Headquarters WORKS_ON SSN PNUMBER HOURS null Fondren,,TX 68 Voss,,TX Castle,Spring,TX 9 Berry,,TX 97 Fire Oak,Humble,TX 6 Rice,,TX 980 Dallas,,TX 0 Stone,,TX PROJECT DEPT_LOCATIONS DNUMBER DLOCATION PNAME PNUMBER PLOCATION DNUM 0 0 Addison Wesley Longman, Inc. 000, Elmasri/Navathe, Fundamentals of Database Systems, Third Edition

3 Figure. Two relation schemas and their functional dependencies. Both suffer from update anomalies. The EMP_DEPT relation schema. The EMP_PROJ relation schema. EMP_DEPT ENAME SSN BDATE ADDRESS DNUMBER DNAME DMGRSSN EMP_PROJ SSN PNUMBER HOURS ENAME PNAME PLOCATION FD FD FD Addison Wesley Longman, Inc. 000, Elmasri/Navathe, Fundamentals of Database Systems, Third Edition

4 Figure. Example relations for the schemas in Figure. that result from applying NATURAL JOIN to the relations in Figure.. These may be stored as base relations for performance reasons. EMP_DEPT ENAME SSN BDATE ADDRESS DNUMBER DNAME DMGRSSN Zelaya, Alicia J. Wallace,Jennifer S. Narayan,Ramesh K. Jabbar,Ahmad V. Borg,James E Fondren,,TX 68 Voss,,TX Castle,Spring,TX 9 Berry,,TX 97 FireOak,Humble,TX 6 Rice,,TX 980 Dallas,,TX 0 Stone,,TX Administration Administration Administration Headquarters EMP_PROJ SSN PNUMBER HOURS ENAME PNAME PLOCATION null Narayan,Ramesh K. Zelaya,Alicia J. Zelaya,Alicia J. Jabbar,Ahmad V. Jabbar,Ahmad V. Wallace,Jennifer S. Wallace,Jennifer S. Borg,James E. Addison Wesley Longman, Inc. 000, Elmasri/Navathe, Fundamentals of Database Systems, Third Edition

5 Addison Wesley Longman, Inc. 000, Elmasri/Navathe, Fundamentals of Database Systems, Third Edition EMP_PROJ SSN EMP_LOCS ENAME PNUMBER EMP_PROJ EMP_LOCS PLOCATION HOURS PNAME ENAME PLOCATION Smith, John B. Smith, John B. Narayan, Ramesh K. English, Joyce A. English, Joyce A. Wong, Franklin T. Wong, Franklin T. Wong, Franklin T. Zelaya, Alicia J. Jabbar, Ahmad V. Wallace, Jennifer S. Wallace, Jennifer S. Borg,James E. PLOCATION SSN PNUMBER HOURS PNAME PLOCATION null Product X Product Y Product Z Product X Product Y Product Y Product Z Figure. Alternative (bad) representation of the EMP_PROJ relation. Representing EMP_PROJ of Figure. by two relation schemas: EMP_LOCS and EMP_PROJ. Result of projecting the populated relation EMP_PROJ of Figure. on the attributes of EMP_LOCS and EMP_PROJ.

6 Figure.6 Result of applying the NATURAL JOIN operation to the tuples above dotted lines in EMP_PROJ and EMP_LOCS, with generated spurious tuples marked by an asterisk. SSN PNUMBER HOURS PNAME PLOCATION Narayan,Ramesh K. Narayan,Ramesh K. Narayan,Ramesh K. Addison Wesley Longman, Inc. 000, Elmasri/Navathe, Fundamentals of Database Systems, Third Edition

7 Figure.7 The teach relation state with an apparent functional dependency text COURSE. However, COURSE TEXT is ruled out. TEACH TEACHER COURSE TEXT Smith Smith Hall Brown Data Structures Data Management Compilers Data Structures Bartram Al-Nour Hoffman Augenthaler Addison Wesley Longman, Inc. 000, Elmasri/Navathe, Fundamentals of Database Systems, Third Edition

8 Figure.8 Normalization into NF. Relation schema that is not in NF. Example relation instance. (c) NF relation with redundancy. DEPARTMENT DNAME DNUMBER DMGRSSN DLOCATIONS DEPARTMENT DNAME DNUMBER DMGRSSN DLOCATIONS Administration Headquarters {,, } {} {} (c) DEPARTMENT DNAME DNUMBER DMGRSSN DLOCATION Administration Headquarters Addison Wesley Longman, Inc. 000, Elmasri/Navathe, Fundamentals of Database Systems, Third Edition

9 Addison Wesley Longman, Inc. 000, Elmasri/Navathe, Fundamentals of Database Systems, Third Edition (c) EMP_PROJ SSN ENAME PNUMBER HOURS EMP_PROJ SSN ENAME EMP_PROJ Narayan,Ramesh K. Zelaya,Alicia J. Jabbar,Ahmad V. Wallace,Jennifer S. Borg,James E. SSN ENAME EMP_PROJ PROJS PNUMBER HOURS SSN PNUMBER HOURS null Figure.9 Normalizing nested relations into NF. Schema of the EMP_PROJ relation with a nested relation PROJS. Example extension of the EMP_PROJ relation showing nested relations within each tuple. (c) Decomposing EMP_PROJ into NF relations EMP_PROJ and EMP_PROJ by propagating the primary key.

10 Addison Wesley Longman, Inc. 000, Elmasri/Navathe, Fundamentals of Database Systems, Third Edition FD FD FD EMP_DEPT ENAME SSN BDATE ED ED ENAME SSN BDATE EMP_PROJ SSN PNUMBER HOURS ENAME PNAME PLOCATION EP EP SSN PNUMBER HOURS SSN ENAME ADDRESS DNUMBER NF NORMALIZATION FD FD FD EP PNUMBER ADDRESS DNUMBER DNAME DMGRSSN NF NORMALIZATION PNAME PLOCATION DNUMBER DNAME DMGRSSN Figure.0 The normalization process. Normalizing EMP_PROJ into NF relations. Normalizing EMP_DEPT into NF relations.

11 Addison Wesley Longman, Inc. 000, Elmasri/Navathe, Fundamentals of Database Systems, Third Edition (c) (d) LOTS FD FD LOTS FD FD LOTSA FD FD PROPERTY_ID# COUNTY_NAME LOT# AREA PRICE PROPERTY_ID# COUNTY_NAME LOT# AREA PRICE LOTS COUNTY_NAME FD PROPERTY_ID# COUNTY_NAME LOT# AREA AREA PRICE LOTS LOTS FD TAX_RATE LOTS LOTSA LOTSB LOTS FD FD NF NF NF FD LOTSB TAX_RATE Figure. Normalization to NF and NF. The lots relation schema and its functional dependencies fd through FD. Decomposing lots into the NF relations LOTS and LOTS. (c) Decomposing LOTS into the NF relations LOTSA and LOTSB. (d) Summary of normalization of lots.

12 Figure. Boyce-Codd normal form. BCNF normalization with the dependency of FD being lost in the decomposition. A relation R in NF but not in BCNF. LOTSA FD PROPERTY_ID# COUNTY_NAME LOT# AREA FD FD BCNF Normalization LOTSAX LOTSAY PROPERTY_ID# AREA LOT# AREA COUNTY_NAME R A B C FD FD Addison Wesley Longman, Inc. 000, Elmasri/Navathe, Fundamentals of Database Systems, Third Edition

13 Figure. A relation TEACH that is in NF but not in BCNF. TEACH STUDENT COURSE INSTRUCTOR Narayan Smith Smith Smith Wallace Wallace Wong Zelaya Database Database Operating Systems Theory Database Operating Systems Database Database Mark Navathe Ammar Schulman Mark Ahamad Omiecinski Navathe Addison Wesley Longman, Inc. 000, Elmasri/Navathe, Fundamentals of Database Systems, Third Edition