Kjeld Svidt  Institut for Byggeri og Anlæg  Aalborg Universitet IT i Byggeriet Semester 6, kursusgang Databaser (1) Kjeld Svidt

Kjeld Svidt  Institut for Byggeri og Anlæg  Aalborg Universitet What is a database? The database can be regarded as an electronic filing cabinet where structured digital data can easily be stored and retrieved. –a collection of data and their relations –the hardware used to store the data –the software used to manipulate and handle the data.

Kjeld Svidt  Institut for Byggeri og Anlæg  Aalborg Universitet Database history (1) Early Hierarchical databases Grows in a tree like structure from the root. Efficient to search but hard to make changes in the structure.

Kjeld Svidt  Institut for Byggeri og Anlæg  Aalborg Universitet Database history (2) Mid 1960 The Network model –Uses the association as its basic unit. It consists of linked independent entities. This database is more flexible than the hiearchical when it comes to introduce new entities but it may be harder to see through than the hiearchical structure.

Kjeld Svidt  Institut for Byggeri og Anlæg  Aalborg Universitet Database history (3) Late 1970 The Relational Database Model (Codd, 1982), "Relational Database: A Practical Foundation for Productivity". Communications of the ACM (Association for Computing Machinery), February 1982, Volume 25, Number 2. Conceptual models independent of underlying data models where not formulated. The implementation data model (Hierarchical, Network or Relational) highly influenced the specification made in the analyses phase of modelling. Chen Peter Pin-Shan, 1976, "The Entity-Relationship Model - Toward a Unified View of Data". DBMS, Database Management Systems, where designed.

Kjeld Svidt  Institut for Byggeri og Anlæg  Aalborg Universitet Why use a database? Avoid duplication of data (non-redundancy) Establish a standardised way to extract adapted and selective data from information containers (both for humans and machines) Efficient maintenance, separate information storage from information presentation Build information containers available to different programs and web-applications

Kjeld Svidt  Institut for Byggeri og Anlæg  Aalborg Universitet Examples of database use Telephone directories Product libraries Customer informatíon Libraries

Kjeld Svidt  Institut for Byggeri og Anlæg  Aalborg Universitet Examples of database use Project webs and model servers for the construction industry Construction models, e.g. –Revit –Archicad –Tekla

Kjeld Svidt  Institut for Byggeri og Anlæg  Aalborg Universitet Stigende marked for databaser Markedet for relationsdatabaser voksede i 2004 med 15% til i alt 15 mia dollars. Kilde: Computerworld,

Kjeld Svidt  Institut for Byggeri og Anlæg  Aalborg Universitet Relationsdatabaser Data opbevares i tabeller Hver række i tabellen udgør en ”post” Hver post består af et antal ”felter” (kolonner Tabeller kobles sammen via ”relationer”

Kjeld Svidt  Institut for Byggeri og Anlæg  Aalborg Universitet Datatyper Tekst Tal, heltal, flydende Tidsangivelse Valuta autonummerering Links til objekter udenfor databasen...

Kjeld Svidt  Institut for Byggeri og Anlæg  Aalborg Universitet Kort intro til Microsoft Access