Databases Flashcards
(25 cards)
Concurrent Access
Many users can access the data. Data is consistent between users.
Data Integrity
The maintenance that the data selected is correct
Throughput
How many actions can be submitted per second
Availability
The amount of users and times that can access the data
Fault Tolerance
The system in place to correct the data should a partial part of the storage be corrupted
Structured Query Language (SQL)
Language used to manage data in a Database Management System (DBMS)
Database Management System (DBMS)
The software package which creates and manages the database.
Declarative
Finding the most efficient way of completing a query
Relations
A collection of attributes making a tables
Data Definition Language (DDL)
Creates and deletes tables
Data Manipulation Language (DML)
Query tables. Insert/Update/Delete
Design Goals
Business rules, throughput, contain all data, readable
Data Quality
Accuracy, completeness, consistency, reliability
Business Requirements
Throughput vs availability
Elements of Database Design
Conceptual modelling, logical design, distributed design, physical design
Cardinality
Constraint on the number of entities in a relationship
Weak Entities
Entities with no primary key. Borrowed part from another entity.
Replace Many-Many
Associate entity with 2 one to many relationships
Instance Diagram
Shows the structure of the relationships between entities
ACID
Atomicity, Consistency, Isolation, Durability
Atomicity
Each set of queries is treated as a single transaction
Consistency
Each transaction will leave the database in a valid state
Isolation
Transactions carried out sequentially or concurrently will produce the same result
Durability
Transactions sent are completed entirely or not at all
