Fundamentals of Databases

• Data Model: An abstract model for organising data and its relationship to real world entities.
• Entity-Relationship Modelling: A method of abstractly describing the data tables and the relationships between them visually. They can be used to reduce redundancy and construct a relational database.
• Composite Primary Key: A primary key made up from two or more other keys.
• Foreign Key: A linking attribute that joins two tables in a relational database by being a primary key in one and a foreign key in the other.
• Primary Key: A unique identifier that identifies each record in a table.
• Relational Databases: A database where separate tables are made for each entity, and relationships between entities are represented by foreign keys.
• Normalisation: The formal process of optimally designing data tables by reducing data redundancy and repetition by converting them into normal forms.
• Second Normal Form (2NF): A table in 1NF that has data that repeats across multiple records removed and put into a new table with appropriate relationships (no partial dependencies).
• Third Normal Form (3NF): A table in 2NF where all attributes that are not the primary key are fully dependent on the primary key (no non-key dependencies).
• SQL: A language for relational database management and manipulation.
• Client Server Database: A system that provides simultaneous access to the database for multiple clients
• Integrity: The idea of keeping a database consistent by ensuring that any changes made to data or relationships associated with a table are accounted for in all the linked tables
• Record Locks: A technique used to prevent simultaneous access to data in a database by locking a record when it is being edited or updated. Otherwise, inconsistencies may aries in the database
• Serialisation: A technique used to preserve integrity by only allowing one transaction to be processed at a time on a client server database
• Timestamp Ordering: A technique to handle concurrent access by executing transactions from multiple users based on the value of their associated timestamp. Each transaction receives a timestamp whenever it begins.