OCR A Level Computer Science - Databases

Flashcards on Relational Databases, Data Normalization, ER Diagrams, Data Management, SQL, Referential Integrity, and Transaction Processing.

Field

A single piece of data in a record.

Record

A group of related fields, representing one data entry.

Table

A collection of records with a similar structure.

Primary Key

A unique identifier for each record in a table.

Compound Primary Key

A combination of two or more fields that is unique for all records.

Foreign Key

A field in a table that refers to the primary key in another table, used to link tables and create relationships.

Secondary Key

A field or fields that are indexed for faster searching.

Database Management System (DBMS)

Software used to manage databases (e.g., MySQL, Oracle, Microsoft SQL Server, PostgreSQL).

Database

An organized collection of data that allows easy storage, retrieval, and management of information.

Indexing

Technique used to speed up data retrieval by creating an index of certain columns.

Flat File Database

Database that stores all data in a single table, leading to data redundancy and inefficient storage.

Relational Database

Database that organizes data into multiple tables, using keys to connect related data and reduce redundancy.

Atomic Values

Each column must contain single, indivisible values.

No repeating groups

Columns must not contain arrays or lists of values

Unique column names

Each column must have a unique name within the table

Unique identifier (primary key)

Each row must have a unique identifier to distinguish it from other rows

Second Normal Form (2NF)

A table must fulfill all 1NF requirements and have full functional dependency.

Full Functional Dependency

All non-prime attributes must be fully dependent on the primary key

No partial dependencies

Non-prime attributes must not depend on only part of the primary key

Third Normal Form (3NF)

A table must fulfill all 2NF requirements and have no transitive dependencies.

No transitive dependencies

Non-prime attributes must not depend on other non-prime attributes

Entity

Something worthy of capturing and storing data about.

Entity Relationship Diagram (ERD)

Diagram that represents the entities (tables) in a database and the relationships between them.

Link Table

A new table created to resolve many-to-many relationships between entities.

Forms

Collect user input and organize data in a structured format, commonly in web applications.

OMR (Optical Mark Recognition)

Detects marked areas on paper using a special machine to read the marks, used for exams and surveys.

OCR (Optical Character Recognition)

Converts printed or handwritten text into digital format, useful for digitizing documents.

Sensors

Devices that detect and respond to changes in the environment, converting physical signals into digital data.

Barcodes

Machine-readable representation of data using parallel lines or geometric patterns, used for tracking items and inventory.

Data Mining

Process of discovering hidden patterns, correlations, and insights from large datasets using machine learning and statistics.

Query By Example (QBE)

User-friendly method for constructing database queries using a visual interface.

CSV (Comma Separated Values)

Simple data exchange format that stores tabular data in plain text, using commas to separate values.

JSON (JavaScript Object Notation)

Lightweight data interchange format that uses key-value pairs and is common in web applications.

Memory Sticks

Portable storage devices that use flash memory to store and transfer data via USB.

Email

Electronic communication system for exchanging messages and files between users over the internet.

SQL (Structured Query Language)

Programming language used to interact with a DBMS to select, insert, delete, and manage data.

SELECT

Retrieves data from a database table.

FROM

Specifies the tables to retrieve data from.

WHERE

Filters the data based on a specified condition.

AND

Combines multiple conditions in a WHERE clause.

OR

Retrieves data when at least one of the conditions is true.

WILDCARDS

'*' and '%' symbols are used for searching and matching data

INSERT

Adds new data to a database table.

DELETE

Removes data from a database table.

DROP

Deletes a table in a database.

Referential Integrity

Ensures consistency between related tables in a relational database by maintaining valid relationships between primary and foreign keys.

CASCADE

Automatically makes changes to related records

NO ACTION/RESTRICT

Prevents changes if related records exist

Transaction

A sequence of database operations treated as a single unit of work.

Locking

Ensures that no two transactions can access the same data simultaneously.

Commit

Saves all changes made in the transaction as permanent.

Rollback

Reverts the changes made in the transaction.

Concurrency Control

Manages simultaneous access to data in a multi-user environment.

ACID

A set of rules that all Database Management Systems (DBMS) must use to ensure data integrity

Atomicity

All operations in a transaction succeed or fail as a whole

Consistency

Ensures data remains in a consistent state after transactions

Isolation

Transactions are isolated from each other.

Durability

Committed transactions persist even in case of system failures

Record Locking

A technique used in database management systems (DBMS) to prevent conflicting access to data by multiple transactions or processes

Shared lock (Read lock)

Allows multiple transactions to read a record simultaneously, but prevents modifications or deletions until the lock is released

Exclusive lock (Write lock)

Allows only one transaction to access and modify a record, blocking other transactions from reading or writing to the locked record until the lock is released