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Relational database
data stored in tables
must put data into the correct tables
define relationship between tables
primary key
Standard Database Notation
EMPLOYEES(EmployeeID, Surname, Forename)…read more

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Creating a database file
Design the record format for a table, considering:
­ the order of the fields;
­ the name of each field;
­ the data type for each field.…read more

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Importance of Data types
Certain field types are automatically validated when the user
enters data.
­ If you have specified the field as a text field, no automatic validation
is possible.…read more

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Primary key
Each record in a database file needs to be given a
unique identifier - the primary key.
It needs to be carefully chosen;
­ Surname, for example, is no use as an identifier.
­ MS Access has an Autonumber data type which generates
unique identifiers automatically
The primary key sometimes consists of more than one
field: for example several stores in a national chain may
each have a store number, and each store may have
Departments 1,2,3 etc.…read more

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Hierarchy of data
­ All data is stored in a computer's memory or storage devices in the form of
binary digits or bits. A bit can be either `ON' of `OFF' representing 1 or 0.
­ is a group of 8 bits. One byte can represent one character or, in different
contexts, other data such as a sound, part of a picture etc.
­ is a group of characters. e.g.…read more


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