Databases

A database is structured collection of data. Thus, card indices, printed catalogues of archaeological artefacts and telephone directories are all examples of databases. Databases may be stored on a computer and examined using a program. These programs are often called `databases’, but more strictly are database management systems (DMS). Just as a card index or catalogue has to be constructed carefully in order to be useful, so must a database on a computer. Similarly, just as there are many ways that a printed catalogue can be organised, there are many ways, or models, by which a computerised database may be organised.

One of the most common and powerful models is the `relational’ model, and programs which use this model are known as relational database management systems (RDMS).

Computer-based databases are usually organised into one or more tables. A table stores data in a format similar to a published table and consists of a series of rows and columns. To carry the analogy further, just as a published table will have a title at the top of each column, so each column in a database table will have a name, often called a field name. The term field is often used instead of column. Each row in a table will represent one example of the type of object about which data has been collected. Table 1(a) (p. [*]) is a an example of a table from a database of English towns. Each row, in this case a town, is an entity, and each column represents an attribute of that entity. Thus, in this table `population’ is an attribute of `town.’

One advantage of computer-based tables is that they can be presented on screen in a variety of orders, formats, or according to certain criteria, all the towns in Hertfordshire, or all towns with a cathedral.

 

[A table of English towns]

town county population county town? cathedral?
Welwyn Garden City Hertfordshire 40,570 no no
St. Albans Hertfordshire 123,800 no yes
Hertford Hertfordshire 2,023 yes no
Durham Durham 29,490 yes yes

[A badly designed table]

town county population county town? cathedral? county population county size
Welwyn Garden City Hertfordshire 40,570 no no 937,300 631
St. Albans Hertfordshire 123,800 no yes 937,300 631
Hertford Hertfordshire 2,023 yes no 397,300 631
Durham Durham 29,490 yes yes 132,681 295
  Essex       1,426,200 1,528

[A table of counties]

county population size (square miles)    
Hertfordshire 937,300 631    
Durham 132,681 295    
Essex 1,426,200 1,528    

———————————————————————————–

Ref: http://www.ucl.ac.uk/archaeology/cisp/database/manual/node1.html

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