database theory

Database theory

• Data normalisation - is a mathematical technique for analysing data and is staged process which improves the data base design at each stage.
• Relational database - a large collection of data items being stored in tables containing links between the tables so that the data can be accessed in many different ways and by a range of different applications program.
• Data warehouse - a huge database specifically structured for information access and reporting.
• Data mining is the analysing of data that's been stored in a data warehouse to find and discover patterns in data.

Flat files

• disadvantages of flat files:
• There is no record of a tool unless it is hired out.
• Even if a customer has hired a tool in the past, their details (customer NO, forename, surname, etc) still need to be re-entered and this wastes time. if you look at the first two rows of the table you can see that it contains some identical data.
• The tool details need to be entered as each customer hires it and this again wastes time.
• There are problems with data integrity. inconsistencies in the data can arise when, for example, the customer changes their address, as some of the old records (i.e. rows in tables) will contain the old details.
• features of flat files
• can be created using spreadsheet or database software
• all the data is held in a single table
• they can suffer from data redundancy
• only useful with simple applications
• very simple to set up
• features of relational databases:
• data is held in two or more tables.
• there are links between the tables.
• data from any of the tables can be extracted.
• greater knowledge is needed to set them up.