OCR Computer Science A Level - 1.3.2 Databases Exam 2024 Questions And Answers 100% Correct

Entity - ANSWERSA category of object, person, event or thing of interest to an organisation about which data is to be recorded Attribute - ANSWERSA named piece of data about a particular entity, with an associated data type. Also known as a field. Flat File database - ANSWERSDatabase consisting of tables which have no links to one another. Each table is entirely standalone. Primary Key - ANSWERSAn attribute which uniquely identifies each entity in a table. Secondary key - ANSWERSAn attribute which can uniquely identify an entity but hasn't been selected as the primary key. E.g. in a customer table, the Customer ID may be the primary key but the email could be considered a secondary key. They often are used to index a table so that searching is quicker. Entity relationships - ANSWERSOne to one One to many Many to many (must be avoided, can use an intermediary table) Entity Relationship Diagram - ANSWERSShow the relationships between the different entities. A single line into a box shows 'one' and three lines in represents 'many'. Relational database - ANSWERSA database with multiple tables which link together through the use of foreign keys. Foreign key - ANSWERSAttribute which creates a join between two tables. It is an attribute that exists as a primary key in the table being linked to. Composite Key - ANSWERSPrimary key which consists of more than one field. Referential integrity - ANSWERSMaking sure that the links between tables are always kept valid when records are added, updated or deleted. E.g. A User makes many IT Requests. If a User is deleted, all its IT Requests should also be deleted. Normalisation - ANSWERSProcess used to come up with the most efficient design for a relational database - No data is unnecessarily duplicated - Data is consistent throughout database - Structure of the table is flexible enough to allow you to enter as many or as few items as required - The structure should enable a user to make all kinds of complex queries relating data from different tables First normal form - ANSWERSTable has a primary key. No duplicate attributes. No repeating groups and no composite attributes. Second normal form - ANSWERSContains no partial key dependencies. A partial key dependency is when an attribute depends on only part of the composite primary key. Must have no Many-to-Many relationships. Must also be in 1NF. Third normal form - ANSWERSContains no non key dependencies. Every attribute must depend on only the primary key and nothing but the primary key. Must also be in 2NF. SQL - ANSWERSStructured Query Language, declarative language used to query and update tables in relational databases. SELECT...FROM...WHERE - ANSWERSUsing the WHERE clause with SELECT...FROM allows you to specify conditions that must be met for data to be se