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Slide 1

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10 Databases
Suppose a school stores information about its students
on record cards. Each student has their own card; this
is their record.
The individual pieces of information recorded on each
card, such as name and date of birth, are called fields.…read more

Slide 2

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Files, records and fields
Information in computer-based filing systems is
stored in data files.
A file is a collection of related records.
Related records means that each record in a file will
contain the same sort of information as all the other
A record must have at least one field.
A field contains one individual item of data.…read more

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Slide 4

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Fixed and variable length records
A fixed length record is one where the length of the fields
in each record has been set to be a certain maximum
number of characters long.
A set amount of storage space is set aside for each field. If
the contents of a field don't fill the space completely it is
remains empty and is wasted.…read more

Slide 5

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The problems with fixed length records are:-
Fields very rarely contains the maximum number of
characters allowed which wastes space.
Values sometimes can't be entered because they are too
large to fit inside the allowed space in a field.
The advantage of fixed length records is that they make
file processing much easier because the start and end of
each record is always a fixed number of characters apart.
This makes it much easier to locate both individual
records and fields.…read more

Slide 6

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A variable length record is one where the length of a
field can change to allow data of any size to fit.
A special marker (# in this example) indicates where each
field ends. The length of a field depends upon the data
that is placed in it. Only the space needed for a field is
ever used -- so none is wasted.…read more

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Miss Morgan


A great resources for covering all you need to know about databases.



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A very kind remark, I must say.



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