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11 Cards in this Set
- Front
- Back
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Data Consistency |
In a database a data item should have a single value. If the same customer had their surname spelt differently in different parts of the database then Data consistency would be broken |
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Data Redundancy |
If the same data item is stored more than once it is said to be redundant. Data redundancy can lead to wasted storage space and inconsistency |
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Data independence |
Data independence refers to separating data from programs. E.G. a common data store managed by a database management system can be accessed via different programs e.g. payroll/sales - each see only the data they need to do their job. |
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Database |
A database stores data in a series of related tables. The data is accessed and processed by a database management system(DBMS) |
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DBMS |
A database management system can be used to structure and manipulate the data in relational files. It may have the following features. Views - Different users may see different parts of the database.This is normally set so that the user just sees the parts they need to do their job. This hides unnecessary data. SQL - A special purpose language used to set up and manipulate data in a database. E.g. SELECT forename, surname, dob FROM student WHERE dob<#01/01/1990# Transaction control - A transaction is a sequence of events that form a complete task. They must be carried out fully or not at all. E.g. transferring money form one bank account to another. First account must be debited, second credited. Both actions must occur. A DBMS may enforce this. |
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Normalising |
Ensuring data is structured in the most efficient way avoiding redundancy and inconsistency. Easier reconstructing of data and data independence. 1NF- Every table contains a primary key. None of the fields can have multiple values (No repeating groups). 2NF- Where there is a composite key. (The key is made from 2 or more fields) non key fields must not depend on justpart of the key. 3NF- There must be no non key dependencies. (Often written as non key fields must depend on the key, the whole key, and nothing but the key.) |
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Flat File |
A single file that contains all the data in the system as opposed ti a relational database that stores data in separate related-tables |
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Data Warehousing |
The gathering of data from one or more sources for analysis. The data must be held securely. |
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Data mining |
Analyzing data in a data warehouse to identify correlations/patterns.Eg A supermarket may analyse data to identify sales trends to determine future advertising targets/identify improved product placement/predict shopping trends EG An insurance company may analyse data to identify possible trends in claims that may relate to fraudulent claims/identify new products/to improve marketing |
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Distributed data |
A single database may have its data spread amongst many servers. e.g. A multinational company may spread its database amongst servers in different countries.Advantage: Having the customer data physically nearer the place it will be used may increase speed |
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Distributed processing |
Some processing tasks can be spread amongst many computers to share the workload. E.g. Project SETI sends data from radio telescopes to volunteers computers for analysing |
