01 - DBMS

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Data independence• logical independencethe external level is independent of the logicallevel– additions or changes to views do not requirechanges to the logical layer– changes to the logic schema that leave the externalschema unchanged are transparent38
Schemes and instances• in every database there exist:• the schema, substantially invariant in time, thatdescribes its structure (intentional aspect): in therelational model, table headers = list of attributenames and their types• the instance, the current values, which can change alsovery quickly (extensional aspect): in the relationalmodel, the "body" of each table39
Page 1 and 2: Lesson 1 - Introduction to database
Page 3 and 4: Structured informationinformation i
Page 5 and 6: What happened earlier?●each appli
Page 7 and 8: DBMS●●●a Database (DB) is a s
Page 9 and 10: Storagedatabase systems use files t
Page 11 and 12: Processing information• goal: to
Page 13 and 14: Shared information• database shar
Page 15 and 16: Information System• data is conce
Page 17 and 18: Data Model• structures to be used
Page 19 and 20: Historical noteshierarchicalmid-60s
Page 21 and 22: Hierarchical model• restricted ty
Page 23 and 24: Relational model• data and relati
Page 25 and 26: Relational model• table = set of
Page 27 and 28: Example of relational DBSTUDENTSMat
Page 29 and 30: Historical notes●mid-80s: first o
Page 31 and 32: The three abstraction levels of a D
Page 33 and 34: A view (external schema)CoursesCour
Page 35: Data independence• physical indep
Page 39 and 40: Schemes andinstancesSTAFFNAME SURNA
Page 41 and 42: Database languages• data definiti
Page 43 and 44: Integrity●The data must satisfy
Page 45 and 46: Security• data must be protected
Page 47 and 48: Restore• To restore a correct dat
Page 49 and 50: DBA Tasks●design definition and d

01 - DBMS

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