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17 Cards in this Set
- Front
- Back
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explain what a Database should do |
.Store information in a systematic way .Create and Edit data structures .Format the data .import/export data from/to other sources .use queries to search for records .Produce reports about the data .Set security on the data |
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define a Database Management system |
Used to organize and control access to the database. .Allows users to create and edit data and provide facilities to search data using query language .Create and maintain data dictionaries .Maintain data integrity .Check passwords allowing only certain users access .Ensure that recovery is possible if data is corrupted |
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explain rules a Database should follow |
.Each row is a record .Each column is a field .No 2 records in a file can be the same as this can cause confusion so each record has a primary key field which uniquely identifies each record |
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define the problems with Flat Files |
.Data is repeated and this wastes memory space (data redundancy) .Data can be inconsistent |
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define a Relational Database |
Created by splitting a flat file into different tables and linking them by using a particular common field in both tables (foreign field). The links can be be one to one, one to many and many to many. Using this ensures data consistency as each item is stored only once so there is no danger in updating it in one place and not another. Data is not redundant as there is no repeated data. Greater security too as the DBMS ensures only authorized personnel can view the database. However it can be complicated to set up. It allows showing information that is relevant to the particular program and not the entire database as it is split up into multiple tables. |
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define an Entity |
Anything about which data is stored |
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define 1st Normal form |
There must be no repeated groups (only one item per field) (Usually involves making 2 tables) |
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define 2nd Normal form |
There must be no partial dependencies (all fields must be dependent on the the entire key field) (composite key fields generally only include themselves). |
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define 3rd Normal form |
There must be no transitive dependencies (no field can relate to the key field by relating to another field) |
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define the method of Normalizing a table |
All fields in the table must relate to the entity except for foreign fields which are key fields in other tables. Many to Many relationships are eliminated by created by making extra tables. |
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define Data Warehousing |
A large collection of data that are stored together for further processing. It also provides an archive for the data. |
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define Data Mining |
The process of analyzing all the data in the warehouse to provide further information. |
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define a Data Dictionary |
Stores the following details about a database: .Names of tables and Fields .Data types of all the fields .Any field formatting information .field validation details .Any relationships between tables |
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define a Query Language |
Used when a user wants to search data (SQL) |
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define the role of the Database administrator |
.designing the database .keeping users informed of changes .maintenance of the data dictionary .implementing database security measures .allocating passwords .providing training to users .ensuring adequate back up procedures |
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define a distributed system |
A system using a number of different computers linked by a network while the user feels they are only using one local computer. |
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define a distributed database |
Stores data on a number of different computers linked by a network. .Large databases can be spread out to different computers .One computer does not get overloaded with a potential large amount of processing requirements .Data inconsistency is probable as data is stored on different systems .Queries may not work if one of the database computers is faulty |
