Databases

  • Created by: Mulla52
  • Created on: 01-06-17 19:04
What is a database?
A database is a persistent (saved on secondary storage for the future) and organised (structured so that it can be easily processed) store of data on a computer system.
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What can errors in databases result in?
Financial loss (e.g if a bank account is wrongly credited), life or death situations (e.g. incorrect navigational data for aircraft) and embarrassment (e.g. sending bills to customers who have died)
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What does data security refer to?
Keeping data safe - data can be lost because of a catastrophe, an accident (e.g. an employee deleting data) or a malicious action (e.g. by an intruder)
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How can data be protected?
Regular backups, restricting access, keeping audits of who has accessed data and having a minor database server so that data is saved in at least two places.
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What does data integrity mean?
How well the data reflects reality. It implies that the data is correct and fit for purpose. It is maximised by validation and software that prevents inconsistent states.
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What is validation?
The process of checking data when it is input and checks that data conforms to certain rules. Examples include length check, type check, range check, presence check etc.
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What is verification?
Checking that the data entered is correct. It can be a simple visual check against the source data.
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What is a view?
A subset of the data in a database. Making suitable views for each staff member increases the efficiency of using the database and reduces risks.
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What does CRUD stand for?
Create, Read, Update and Delete.
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What does data matching do?
It compares different databases to look for particular relationships.
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What does data mining do?
It looks in many different unrelated databases. It may show up unexpected relationships that may not have been noticed before.
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Describe the structure of a flat file database.
This is just rows and columns - each row is called a record and each column is called a field.
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What is the main disadvantage of a flat file database?
Data might be repeated unnecessarily - unnecesary repetition is called data redundancy. This can lead to inconsistent spellings which can cause problems when searching for data.
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What is a relational database?
Data is stored in separate tables and the tables are linked together so that related data can be easily extracted. Each table is called an entity.
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What is the DBMS?
The Database Management System is software that looks after a database at a fundamental level.
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What does the DBMS allow database administrators to do?
It is a general-purpose tool that enables database applications to be created, data to be protected and kept consistent and accurate and queries can be run to extract data.
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Why is it important to separate data from applications?
So that programmers don't have to worry that their applications might damage existing data structures, new applications can be written without restructuring the data and data can be more easily shared between applications.
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What is a transaction?
A transaction refers to when a change takes place in a database. Transactions must not damage the integrity of a database.
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What is a primary key?
A primary key uniquely identifies a record (row). It can be one field or a combination of fields. Each field has to be a particular data type.
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How are tables linked together in a relational database?
The primary key of one table can be linked to the foreign key of another table. This allows data to be stored only once which avoids data redundancy and reduces the risk of errors.
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What are forms?
Forms provide a friendly user interface. Data can be input into tables from forms or selected data can be output to the screen in a form. Forms can have objects, such as buttons and drop-down lists to make them easier to use.
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What are reports?
Reports are output from a database. They can be set up to summarise, group and select data.
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What is a query?
A query is used to extract a subset of data in a database. Queries can combine data from more than one table and present it in whatever order is required.
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What is a database module?
A database module is a unit of software that takes care of some particular functionality of a database.
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Other cards in this set

Card 2

Front

What can errors in databases result in?

Back

Financial loss (e.g if a bank account is wrongly credited), life or death situations (e.g. incorrect navigational data for aircraft) and embarrassment (e.g. sending bills to customers who have died)

Card 3

Front

What does data security refer to?

Back

Preview of the front of card 3

Card 4

Front

How can data be protected?

Back

Preview of the front of card 4

Card 5

Front

What does data integrity mean?

Back

Preview of the front of card 5
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