1.3.2 Databases Flashcards
What is a primary key?
A field that uniquely identifies a record in a table
What is a foreign key?
The linking field in a foreign table, formed when a relationship between 2 databases is formed. The Foreign Key becomes the Primary Key of the new table
What is a secondary key?
An index field other than the primary key used to search and sort through the database in a different order or with more speed/convenience
What is normalisation?
The process of arranging data into tables and setting their relationships to make the best layout for a relational database
What is an entity?
An entity is an object of interest to an organisation around which data is to be recorded
What are the criteria for the 1st normal form?
- All field names must be unique
- Values in fields must be from the same domain
- Values in fields must be atomic
- No 2 records should be identical
- Each table needs a primary key
What is a composite key?
A combination of 2 or more fields that can be used to uniquely identify each record
What are the criteria for 2nd normal form?
- Data is already in 1st normal form
- Partial dependencies are removed
What is a partial dependency?
When one or more fields depend on only part of the primary key (normally when the primary key is composite)
What are the criteria for 3rd normal form?
- Data is already in 2nd normal form
- Transitive dependencies are removed
What is a transitive dependency?
Where the value of a field is determined by the value of another field that is not part of the primary key
What is an index?
A data structure used to look up and access data in the database quickly
What is referential integrity?
A process for ensuring consistency of the data in a database
What does ACID stand for?
Atomicity, Consistency, Isolation, Durability
What does Atomicity mean in ACID?
A transaction must be processed in its entirety or not at all
