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Keywords
· Flat File ­ A database containing a single table to store data.
· Relational Database ­ A database containing multiple tables which are linked together, known as relationships.
· Data Redundancy ­ A central bank of data that can be used by multiple databases and other software without
duplication.
· Data Consistency ­ Separate files containing the same data which has to be individually updated for it to be up
to date.
· Data Integrity ­ The measure of data correctness.
· Data Independence ­ When the data and the data processing software are separate.
· Data Dictionary ­ A store of information about data e.g. tables, validation and field names.
· Primary key ­ Used to define a record in a table.
· Foreign key ­ A Primary key in one table linked to another.
· Relational Link ­ When 2 or more tables contain the same field.
· SQL (Structured Query Language) ­ A language used for extracting information from databases.…read more

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Database Characteristics
Flat File Database Relational Database
· Contains a single table · Contains many tables
· Data is repeated (Duplication) · Data repetition is limited
· Space inefficient · Space efficient
· Data may be inconsistent · Links between tables
· Can be produced in a · Software compatible and
spreadsheet or database suitable for mail merge
package…read more

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Data Validation Techniques
Data validation is applied to a field to retain consistency and format at each
entity of a field ­ E.g. <10 (Less than 10)
· A length check restricts the data entry to a minimum, maximum or exact
length and can be formatted using < > = symbols
· A range check restricts the data entry to a value within a range or within a
range inclusive of the given values using < > =
· An input mask restricts the data entry to either letters, numbers or a
combination in a given order using `L' for Letter, `0' for Number, `&' for a
space... or date and currency values such as 00/00/0000
· A lookup restricts the user to choose a value from a drop down list, the
source can be entered manually in the set-up wizard or can be based on an
existing table in a database…read more

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Relational Links
· A relational database has relational links, hence the name
· The links are between common fields such ­ i.e. A field that appears in
organic one table and foreign in another
· The relational links can be shown in an entity relationship diagram
· There are different types of relational link...
· A One-to-one link is where there can only be one common entity for the field
· A One-to-many (Or vice versa) link is where there can be a single entity in one field,
but many in the other
· A Many-to-many link is where there can be many entities in both organic and
foreign fields
· The example on the next page shows a One-to-many relationship between
Students and Loans... A student can take out many loans but each loan can
only belong to one student, therefore it is a one to many relationship…read more

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Entity Relationship Diagram
· An entity relationship diagram is The diagram should contain the following features
where appropriate:
a hand draw or computerised
plan showing each table with #Name Indicates a foreign key
fields and its links to other tables
Name Indicates a primary key
· For example:
One-to-one relationship
tbl1Students tbl2Loan
StudID #StudID
LoanID
One-to-many relationship
StudGrp
Forename LoanDate
Surname DueDate Many-to-many
Authorisation relationship…read more

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