MicroSoft SQL-server Some walk through
lv/ Figures & some text from: © Pearson Education Limited 1995, Functions For a DBMS #1 Data storage, retrieval and update A user-accessible catalogue Transaction support Concurrency control services Recovery services
lv/ Figures & some text from: © Pearson Education Limited 1995, Functions For a DBMS #2 Authorization services Support for data communication Integrity services Services to promote data independence Utility services
Database – not a single system
MS-SQL – Architecture
Database – Process organisation
Databases - system and user
lv/ Figures & some text from: © Pearson Education Limited 1995, DBMS: ANSI-SPARC
Example
lv/ Figures & some text from: © Pearson Education Limited 1995, Description of the 3 levels #1 External Level – Users’ view of the database. – Describes that part of database that is relevant to a particular user. Conceptual Level – Community view of the database. – Describes what data is stored in database and relationships among the data.
lv/ Figures & some text from: © Pearson Education Limited 1995, Description of the 3 levels #2 Internal Level – Physical representation of the database on the computer. – Describes how the data is stored in the database.
Entity integritet - Normalisering Afværge – Insert anormalitet – Delete anormalitet – Update anormalitet Hvordan – NF1: primær nøgle + kun én værdi i hver ‘celle’ – NF2: NF1 + del af primær nøgle IKKE alene udpege andre felter i rækken – NF3: NF2 + kun primær nøgle udpege felter i rækken
Refential Integritet Ved fremmed nøgler – Ved delete eller update Default Null Cascade No Action