Unit 8-databases
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File based approach
Data stored in files with separate data items stored in different places for certain topics
Field
One item/column about one thing, E.G.one column for student names
Primary key
Unique identifier
Table/relation
All the data about one entity
Record/tuple
Data in one row of the table
Relational database
Similar to file base structure but recorded into tables
Attribute
Column/field in the table
Data item
Individual data thing
Candidate Key
Unique Identifier
Secondary key
Alternative primary key that wasn’t chosen for some reason
Foreign key
Attributes of one table that link to the primary key of another table
Composite key
Made up of two un-unique attributes to make a new, unique attribute
Advantages of a relational database
Data redundancy reduced Data only changed once and is automatically updated everywhere Data independent of the app.s, so doesn’t affect them and makes it more easily available
Data management
Organising and managing the DBs data
Data dictionary
Contains the DB metadata
Logical schema
Specific database model used to build DB and independent from the DBMS
Data modelling
Way of showing DB structure like E-R diagrams
DBMS
Provides security like: Access rights that’s limited based on user Automatic audit trail Usernames and (strong) passwords Data encryption Regular backup Also uses query processors and developer interface (using SQL)