9.1 Databases

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Data Types

There are a number of data types that are represented in a database:

• Text (e.g. NG321AE)

• Character (e.g. X)

• Boolean (e.g. True)

• Integer (e.g. 15)

• Real (e.g. 19.33)

• Date / Time (e.g. 180555)

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Primary Keys

Each table has a primary key. It acts as a unique number. Duplicate data items would be deleted if entered into the primary key field. It identifies each individual record.

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SQL

Command	Explanation
SELECT	Which fields you want to display
FROM	The table where the data is stored
WHERE	The search criteria
ORDER BY	The data is ordered with rules
SUM	To add numerical data
COUNT	To count the items of data
ASC	Order in ascending order
DESC	Order is descending order
*	Use all fields
<>	Equal to

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Exam Questions

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