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Definition
| A collection of data that is structured so that it provides all necessary access to each unit of data in order to fulfil the differing needs of the user |
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| A Database Management System is the software that makes the database easier to use, manipulate and maintain. |
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| This is the forms, reports, queries etc that are created in order to access a database for a particular purpose. |
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| An Entity is an object that is meaningful in iteself. Eg. Information about a student such as name, address and contact info together are an entity. |
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| This is one set of data - Eg. about one student. |
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This is a characteristic of an entity. Eg. just the student's name or just the name of a book would be an attribute.
An entity can have the attributes in brackets:
BOOK(ISBN, Title, Author, No of Pages, Type) |
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The Key of an entity is the attribute(s) that uniquely identify one occurance.
In the previous example, the ISBN number of the book would be unique to each book title. |
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| These exist between pairs of entities and represent some natural structure in the data. |
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The database scheme is the collection of entities, attributes and relationships that describe the database.
(Everything in the database) |
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| A subset of the entities, attributes and relationships of a database which describe the requirements of a database application. |
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| In an integrated file system each application within a company would have its own set of data. This is making sure all the data is the same accross all the companies. |
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| In a conventional filing system data can be stored more than once in a system - either because its needed by more than one system or because it makes processing easier. Data Redunancy will eliminate uneeded duplicated data. |
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| In a database system the database itself is said to be independant of the application programs that use the media on which it is stored. |
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Definition
| Access to the database is through the DBMS, the DBMS can control which applications can see which parts of the database. |
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Term
| Relational Database Organisation |
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Definition
There are other types of database besides those called relational databases. Two others are hierarchial databases and network databases.
Relational Databases organise data into tables, each table contains information about a particular entity and entities can be related to eachother through common fields between tables. |
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