Databases Flashcards
What is a Relational Database
A database which recognises the difference between entities and uses different tables for each entity
What is an entity
An item of interest about which information is stored
What is a flat file?
A database that consists of a single file, usually about one entity
What is a primary key
A unique identifier for each record in a table
What is a foreign key
The attribute which links two tables together
What is a secondary key
An index other than the primary key used to search and sort through the database with more convenience and speed
What is normalisation
This is the process of coming up with the
best layout for a relational database
What does normalisation try to accomplish
● No redundancy (unnecessary duplicates)
● Consistent data throughout linked tables
● Records can be added and removed without issues
● Complex queries can be carried out
What is an index
An index is a data structure used to look
up and access data in database quickly
What does capturing data mean
Capturing data is the process of getting the information you wish to use
What does selecting data mean
Selecting data is the process of reducing excess information to obtain only the data you require
What does managing the data mean
Managing the data means to manipulate the information in any type of way such as through sorting through it or selecting certain parts using SQL
What is the most common language used to manipulate data in databases
SQL
What are the requirements to be in first normal form
- Contain atomic values
- Have no repeating groups
- Have unique column names
- Have a unique identifier (primary key)
What are the requirements to be in second normal form
- The database is in first normal form,
- There are no partial dependencies (no
composite keys)
What are the requirements to be in third normal form?
- The database is in second normal form.
- There are no non-key dependencies
What does SQL stand for?
Structured Query Language
What is SQL
A declarative language used to manipulate databases
What is referential integrity
The process of ensuring consistency as it makes sure that information is not removed if it is required elsewhere in a linked database
What is a transaction defined as
A transaction is a single operation executed on data
What does ACID stand for
Atomicity, Consistency, Isolation, Durability
What does Atomicity (in ACID) mean
A transaction must be processed in its entirety or not at all
What does consistency (in ACID) mean?
A transaction must maintain referential integrity rules between linked tables.
What does isolation (in ACID) mean?
Simultaneous execution of transactions should lead to the same result as if they were executed one after the other
What does durability (in ACID) mean?
Once a transaction has been executed it will remain so regardless of the circumstances
What is record locking
Record locking is the process of preventing simultaneous access to a record.
What is the name of an issue that can arise as a result of record locking
Deadlock
What is redundancy
The process of creating more than one copy of data in a physically different location
