6. user a user i /program j program x sub-schema a sub-schema i sub-schema z conceptual schema physical schema 3 Level Architecture Databases
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12. user a user i /program j program x sub-schema a sub-schema i sub-schema z conceptual schema physical schema DDL SDDL DML/SQL Practitioners: DBA Users Databases
32. Relationship Rows in one or more tables are associated with each other solely through data values in columns (no pointers). Foreign Key Primary Key Primary Key D-No D-Name M-No 4 Finance 857 7 Sales 179 Primary Key Department Employee E-No E-Name D-No 179 Silva 7 857 Perera 4 342 Dias 7
33. Relational DB Server Architecture Conceptual Layer Physical Layer System Catalogue Base Tables External Layer Stored Tables ... View View View
34. External Model Name Designation Department De Silva Manager Personnel Dias Programmer Computer Perera Chief Accountant Accounts Silva Clerk Accounts View Table Employee Details View View View
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36. External Model User Views Personnel Employee … Department Production Product … Supplier Sales Customer … Product View View View View View View View View View
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38. Conceptual Model Table Table Table E-No Name Designation DOB D-No 01 Dias Programmer 12-05-1956 COM 02 Perera Chief Accountant 15-12-1958 ACC 03 De Silva Manager 01-01-1960 PER 05 Silva Clerk 25-09-1965 ACC Base Table Employee
39. Personnel Employee … Department Production Product … Supplier Sales Customer … Product Employee Department Product Customer Table View View View View View View View View View Table Table Table