Databases

loz .
Mind Map by loz ., updated more than 1 year ago
loz .
Created by loz . about 5 years ago
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A level Computing Mind Map on Databases, created by loz . on 02/09/2015.

Resource summary

Databases
1 A key feature of every table is that it has a 'primary key' for every record. A primary key provides a way to uniquely identify every record in a table.
2 A foreign key is used to link tables together and create a relationship. It is a field in one table that is linked to the primary key in another table.
3 Referential integrity forces the rule that a primary key cannot be duplicated in a table. It also ensures that if the primary key one table is changed, then the foreign keys in the other tables are also updated.
4 Rules can be put in place that forces field data to be in a certain format. For example, a date field may have to use dd/mmm/yyyy i.e. 02/Sep/2007 and not Sep 2nd 07 for example. This is called data validation
5 A relational database can avoid data duplication. It is made up of two or more tables. Tables are related to one another Each record in a table has a primary key. A foreign key provides a link between records in different tables. Data integrity ensures that data remains conistent across tables.
6 Check digit - the last one or two digits in a code are used to check the other digits are correct. Lookup table - looks up acceptable values in a table
7 Format check - checks the data is in the right format. Presence check - checks that data has been entered into a field
8 Length check - checks the data isn't too short or too long. Range check - checks that a value falls within the specified range
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