Database Revision

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DATABASE REVISION Jordan Curnow	Image: 68e9e26c-16f8-43e3-bea2-e11808dbd9e9 (image/jpg)
KEYWORDS AND DEFINITIONS	DATABASES....
Database	An organized collection of data.
Table	Stores all of the records for a particular category.
Record	All of the data or information about one person or one thing.
Field	One piece of data or information about a person or a thing.
Report	Is a collection of data with specific details to analyse.
Primary Key	It is important that every single record in a database has something to uniquely identify it and this is called the 'Primary Key' or sometimes called the 'Key Field'.
DATA TYPES	Image: 38ef800e-e0e2-41b3-92f4-8f311bf69c89.gif (image/gif)
Alphanumeric or Text	This allows you to type in text, numbers and symbols.
Currency	This automatically formats the data to have a £ or $ or Euro symbol in front of the data and also ensures there are two deciaml places.
Auto Number	This data type will automatically increase by 1 as records as added to the database.
Number	This allows a whole number or decimal number. Only numbers can be entered, no letters or symbols.
Date/ Time	This restricts data entry due to a true date. It checks that a data can actually exist, for example it would not allow 31/02/06 to be entered. It formats the data into long, medium or short date/time.
Logical, Boolean, Yes/No	This data type is often reffered to as different things, you may hear it called, "Logical", or "Boolean" or "Yes/No". All it means is that the data is restricted to one of only two choices.
VALIDATION	Type check, range check, presence check and format check.
It is very important to remember that Validation cannot stop the wrong data being entered, you can still enter "Smith" instead of "Smith" or "Brown" instead of "Green" or "78" instead of "87".	What validation can do, is to check that the data is sensible, reasonable and allowable.
PAPER DATABASE EXAMPLES	Telephone book Yellow pages Old library
ELECTRONIC DATABASE EXAMPLES	Modern School Registers Google Facebook
FLAT FILE DATABASE	A database that contains only one table: This table might seem pretty logical at first. But think about it …. Every single time the pet has an appointment, the customer's title, surname, street, town, county, and phone number have to be entered. Also, the pet's name, type and D.O.B. also have to be entered. That would get fairly tedious having to enter so much data each time and there would be a great risk of making a mistake. It also means you have a lot of duplicate data (redundant data) taking up space on your hard drive.
RELATIONAL DATABASE	In this database the data is split up into sensible groups i.e. customer data, pets data and appointments data. Then a separate table is made for each group. The main benefit of a relational database is that data doesn't have to be duplicated. When a customer books an appointment for their pet, a new record is created on the 'appointment's table' and the relevant Customer and Pet IDs are chosen.
DATA DUPLICATION	Data deduplication is a technique for reducing the amount of storage space an organization needs to save its data. In most organizations, the storage systems contain duplicate copies of many pieces of data.
DATA REDUNDANCY	Data redundancy leads to data anomalies and corruption and generally should be avoided by design; applying database normalization prevents redundancy and makes the best possible usage of storage. At the same time, proper use of foreign keys can minimize data redundancy and chance of destructive anomalies.

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