Software Development Unit 2 Databases. What is a database?. A collection of data organised in a manner that allows access, retrieval and use of that data. Data is a collection of unprocessed items, which can include text, numbers, images, audio and video.
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Most organisations realise that data is one of their more valuable assets, because data is used to generate information.
An electronic database allows you to define the data including its:
Allows you to:
Allows you to
A DBMS is the program that creates the database and can manipulate the data within it.
A database defines each field by a number of characteristics such as field size and data type.
A relational database is a database that stores data in tables that consist of rows and columns. Each row has a primary key and each column (field) has a unique name.
The common column (field) is often linked by a unique ID number that is assigned to each record.
Tables in a relational database can be linked in a variety of ways (relationships):
2. The most common relationship is a one-to-many relationship.
3. A many-to-many relationship means that for each record in the first table, many records are required in the second table AND for each record in the second table, many records are required in the first table.
Data can be (by human error,equipment failure problems with the software or by a catastrophe eg fire or flood):
For these reasons data security measures are essential. These measures include:
1. Backing up the data on a regular basis – making a copy of the entire database.
- Data can be backed up daily, weekly, monthly or continuously.
2. Attempting to eliminate factors that cause accidental losses.
3. Preventing unauthorised access to data which can result in it being stolen, misused or corrupted eg