Database

data dictionary

• Stores metadata about the database

Items stored in a data dictionary

• Table name 
• Field name
• Data type 
• Primary key

Purpose of Query Processor

• Allow user to enter criteria
• Searches for data which meets criteria entered

Purpose of Developer Interface

• Enables developer to create user friendly forms and reports

Tasks that can be performed with DBMS

• Create a table
• Create a form
• Create a report

Logical schema

• Provides an overview of database structure 
• Models the problem the database is intended to manage

Levels of the schema

• External : represents the individual's view of the database

• Physical/Internal : Describes how the data will be physically stored

• Logical : How the relationships will be implemented in the logical structure of database

• Conceptual : Describes the views which users of the database might have

Referential Integrity

• Data between linked tables is consistent

Query Processor

 Part of DBMS that allows user to search for data

 Primary Key

Attribute that uniquely identifies each tuple

Secondary Key

Attribute that could be primary key but not selected to be primary key

Foreign Key

A Field in one table that links to a primary key in another table

Attribute

A data item, represented as a field within a table

Entity

Concept in the system that we want to model and store information about

Difference between Security and Privacy of Data

 Security is keeping data safe 
• From accidental loss
• E.g. Need for security

• Privacy is the need to restrict access to personal data
• To avoid it being seen by unauthorised people
• E.g. of need for privacy

Physical measures

• locked doors 
• access by secure methods such as, biometric scans

Firewall 

• stop unauthorised access gaining access to network

Access rights 

• Only relevant people can access certain part of data
• can be read only, or full access / read, write and delete

Password

• Prevents unauthorised access

Anti-Malware 

• To remove/detect virus 
• carry out regular scans

Encryption

• Data meaningless to third party 
• Accessed only by those with decryption key

Auto Backup 

• Create regular copies of data in case of loss 
• can be restored if lost/corrupted

Advantage of using Relational Database to File-based 

 data duplication is reduced

better security

 better data integrity

Disadvantages of File Based

• Data duplication
• Lack of data privacy
• Lack of data integrity