1.3.2 databases

• An organised collection of data (persistent organised store of related data)

• easier + quicker adding, modification, deletion, updating and searching • easier to back up data • can be accessed by multiple people at the same time from different locations

• information stored which can to be personal in some cases • it can be collected and analysed

• facts and details about a certain thing in context.

• something humans obtain/acquire and remember by reading or searching up topics to broaden understanding.

• Where data is stored in tables grouped by entity and linked (related) together.

• link between tables • we need a common field in both tables for relationship to work

• one-to-one • one-to-many • many-to-many

• entity-relationship diagram (ERD) • can also call it entity-relationship model

• A database with multiple independent tables or single table • no links/relationships between tables • suitable to store small amount of data e.g contact details, small product database, maintain game/music collection

• a comma-separated values file (CSV)

• simple + require little expertise to maintain • quick to set up • all records stored in one place

• no links –> inefficient • can become difficult to maintain, expand in future and update, less secure • not easy to query - searching slower • data can be easily duplicated (take up unnecessary storage space due to redundancy)

• Data Integrity maintains consistency, accuracy and reliability of data • referential integrity can be enforced which improves data integrity • Linked tables makes it easier to query, add, modify, delete, update, search and manage/maintain • Easier to change format • Provides security features - keeping data secure is of high importance • Normalised to 3NF • Ensures less data duplication therefore less redundant data reducing file size

• more difficult to set up and need more technical expertise to do things like normalisation • data spread out between multiple table. some tables may be link tables which only display key fields / references • more expensive as DBMS required

• field in a table that is unique for every record

• primary key ensures that each record is distinct from the others.

• it’s the unique primary key field of one table that is stored in another for purpose of creating a link between the tables. (linking field in a table that is a primary key in a related table)

• primary key • table

• there must be a primary/foreign key pair.

• more than one attribute

• none of the attributes on their own (Subject and StudentID) can be guaranteed unique. • But, a student can only enrol for a subject just once so combination of  Subject and StudentId will be unique. • Combining these two attributes will form a composite primary key. (to uniquely identify a record)

• a field by which records are likely to be searched and is therefore indexed

• process of creating a linked list (database index) to improve speed of data retrieval operations on a dataset table at the cost of additional writes and storage space to maintain the index data structure.