Term | Definition |
Foreign key | A foreign key is a primary key from one table; appearing in another table; used to form links between tables. |
1NF | no repeating groups of attributes. |
Data warehouse | A data warehouse is a large collection of data stored together logically for further processing. Examples: An insurance company might use data warehousing to check claims histories together with other insurance companies’ data to try to detect fraud. |
Data mining | Data mining is the analysis of a (large) amount of data in a data warehouse. Example: A supermarket might use data from a loyalty card scheme to send information to particular customers with special offers etc. |
Primary key | A primary key is a field which uniquely identifies a record in a database, for instance in a membership database membership-number might be used to uniquely identify each member. |
3NF | Third normal form means that data items are dependent on the whole key and nothing except the key (or the key, the whole key and nothing but the key). |
Data duplication/redundancy | (storing of the same data more than once) is likely to occur if a database is not normalised. |
Flat File System? | A flat file system may contain a number of single tables with no links between them, whereas a relational database normally contains a number of linked tables (/relations). |
Why normalise a DB? | data independence; reduces data duplication / redundancy; reduces the danger of inconsistency / improves data integrity; reduces the danger of data being lost during update. |
Database administrator | A database administrator is the person in a company who is responsible for the structure and management of the database system and the data in it. |
Database Management System (security) | The DMBS may allow certain users read and/or write access to certain records or fields only. |
Why is an index often used by a database management system? | An index is used to improve read access times to records, and also to sort the records for viewing. |
Distributed database? | Databases often contain huge amounts of data. It is often more efficient to store data on a number of different computers (probably in different locations) to maximise performance. |
State two advantages of a relational database over a flat file system. | Redundancy (data duplication) is reduced (therefore saving space); Risk of inconsistent data is reduced (better integrity of data); Data independence allows different views of the same data. |