Relational Database Concepts

eleanorbradbury
Mind Map by , created over 6 years ago

A2 ICT (5. Relational Database Concepts) Mind Map on Relational Database Concepts, created by eleanorbradbury on 04/11/2013.

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eleanorbradbury
Created by eleanorbradbury over 6 years ago
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Relational Database Concepts
1 data base terminology
1.1 tables- contain data about items, made of rows and columns they must have unique names
1.2 records - single row within a table, contains data about a single item or event
1.3 fields - idividual items of data in a record, also know as attributes
1.4 keys - primary key, single field that is a unique ID for the record
1.5 composite primiary key - where two or more fields make up the primary key
1.6 foreign key - primary key in another table, field in another, used to join the two together
1.7 secondary key - used to index a field
2 entities
2.1 single objects or processes
2.2 information about things
2.3 each entity becomes a table
2.4 entities linked by relationships
3 relationships
3.1 links between entities/tables
3.2 one to one- where one record in a table is linked to only one record in another table
3.3 one to many - one record in a table is linked to many records in a second table
3.4 many to many - the many link goes both ways between two tables
4 referential integrity
4.1 ensuring that for every record in a table with a foreign key, there is a record in the corresponding table with the primary key
5 normalisation
5.1 process applied to data structures
5.2 decreases redundancy
5.3 increases integrity
5.4 first normal form
5.4.1 every data value is atomic
5.4.2 no repeating data
5.4.3 primary key
5.5 second normal form
5.5.1 must be in 1NF
5.5.2 non-key attributes are dependant on the entire primary key
5.6 third normal form
5.6.1 in 2NF
5.6.2 no functional dependancy between non-key items
5.7 advantages of normalisation
5.7.1 removes redundancy
5.7.2 increases consistency
5.7.3 increases integrity
5.7.4 easier maintenance
5.7.5 flexibility for future expansion
5.8 disadvantages of normalisation
5.8.1 reduced database performance
5.8.2 problems with hostorical calculations
6 data dictionary
6.1 database about a database
6.2 contains design details about the database
6.3 includes table name, field name, data type, length, validation, relationships, security
7 datatypes
7.1 text/string - anything not requiring a calculation
7.2 integer, whole numbers only, not telephone numbers
7.3 real, numbers with decimal places
7.4 boolean - one of two values
7.5 date/time - store age , dates, times
7.6 look to see what the data will be used for
8 parameters
8.1 simple query
8.1.1 query where there is only one parameter
8.2 complex query
8.2.1 a query with more than one parameter
8.2.2 makes use of AND, OR and NOT to join paramters
8.3 static
8.3.1 parameter is hard coded into the query and cannot be changed by the end user
8.4 dynamic
8.4.1 request for the parameter given to the end user at run time usually by a dialogue box

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