1
Q
What is a database?
A
- An organised collection of data
- It allows easy storage, retrieval and management of information
2
Q
What are the benefits of electronic databases?
A
- Easier to add, delete, modify and update data
- Data can be backed up and copied more easily
- Multiple users, from multiple locations, can access the database at the same time
3
Q
What is a field?
A
- A single piece of data in a record
- Columns
4
Q
What is a record?
A
- A group of related fields, representing one data entry
- Rows
5
Q
What is a table?
A
- A collection of records with a similar structure
6
Q
What is a primary key?
A
- A unique identifier for each record in a table
- Usually an ID number
- The primary key for all different entries MUST be different
7
Q
What is a compound primary key?
A
- A combination of two or more fields that is unique for all records
8
Q
What is a foreign key?
A
- A field in a table that relates to the primary key in another table
- Used to link tables and create relationships
9
Q
What is a secondary key?
A
- A field or fields that are indexed for fast searching
10
Q
What is a database management system (DBMS)?
A
- Software used to manage databases
11
Q
What is indexing?
A
- Indexing is a technique used to speed up data retrieval in a database
- Certain columns can be indexed so the DBMS does not have to look at every single record during a search
12
Q
What is a flat file database?
A
- One that stores all data in a single table
- It’s simple and easy to understand but causes data redundancy, inefficient storage and is harder to maintain
13
Q
What is a relational database?
A
- One that organises data into multiple different tables
- It uses keys to connect related data which reduces data redundancy, makes efficient use of storage and is easier to maintain
14
Q
What is normalisation?
A
- The process of organising a database to reduce data duplication and improve data accuracy and consistency
- Enhances data efficiency and maintainability
15
Q
What is required for first normal form (1NF)?
A
- Contain atomic values (each column in a table must contain single, indivisible values)
- Have no repeating groups (columns must not contain arrays or lists)
- Have unique column names
- Have a unique identifier (primary key)
16
Q
What is required for second normal form (2NF)?
A
- Must be in first normal form
- Only apply to tables with a compound primary key (more than one primary key)
- Have full functional dependency: all non-prime attributes must be fully dependent on the primary key
- Have no partial dependencies: non-prime attributes must not depend on only part of the primary key
17
Q
What is required for third normal form (3NF)?
A
- Fulfil all second normal form requirements
- Have no transitive dependencies: non-prime attributes must not depend on other non-prime attributes
- Each non-prime attribute MUST depend on the primary key
- Have separate tables for attributes with transitive dependencies, and the table should be linked using a foreign key
18
Q
What is an entity?
A
- Something worth of capturing and storing data about
- Entities become tables in relational databases
- Relational databases store different entities in different tables
19
Q
What are the different types of entity relationships?
A
- One to one
- One to many
- Many to many
20
Q
What is resolving many to many relationships?
A
- Many to many relationships can not exist in an actual database and need to be resolved
- This involves creating a new table known as a “link” table that goes between the identities
21
Q
How can data be captured?
A
- Forms
- Optical mark recognition (OMR)
- Optical character recognition (OCR)
- Sensors
- Barcodes
- Data mining
22
Q
What is optical mark recognition?
A
- Detects marked areas on paper by using a special machine to read marks
- Used for exams, surveys and lottery tickets
- Automates data collection and entry
23
Q
What is optical character recognition?
A
- Converts printed or handwritten text into a digital format
- Useful for digitising documents
- Assists in searching and editing text
24
Q
How do sensors work in data collection?
A
- Devices that detect and respond to changes in the environment
- Convert physical signals into digital data
25
How do barcodes work in data collection?
- Machine-readable representation of data using parallel lines of varying widths and spacing
26
What is QBE in data selection?
- Query by example
- Allows users to search for data by providing an example of the desired output
27
What are some common query operations?
- FIltering
- Sorting
- Joining
- Aggregation
28
Pros and cons of QBE?
- Pros: easy to learn, visual interface makes it simple to understand, provides a more accessible way to perform database searches
- Cons: less powerful and flexible than SQL, may not support advanced database features, can be slower than SQL queries
29
What is CSV?
- Comma Separated Values
- Simple data exchange format
- Stores tabular data in plain text
- Uses commas to separate different values
- Widely supported and easy to parse
30
What is JSON?
- JavaScript Object Notation
- Lightweight data interchange format
- Human-readable and easy to analyse
- Uses key-value pairs
- Common in web applications
31
What is an EDI?
- Electronic Data Interchange
- Standardised electronic communication method
- Transfers documents and data between businesses
- Reduces paper usage and manual processes
- Streamlines transactions and increases efficiency
32
What is an API?
- Application Programming Interface
- A set of protocols that allow different software applications to communicate with eachother
- Facilitate data exchange between applications and platforms
33
What is referential integrity?
- Ensures consistency between related tables in a relational database
- Maintains valid relationships between primary and foreign keys
- There must not be foreign keys for which a matching primary key in a linked table does not exist
34
What are the constraints of referential integrity?
- A foreign key must either:
- Match a primary key in a linked table
- Or be null
35
Cascade actions for referential integrity
- CASCADE: automatically makes changes to related records
- SET NULL: sets foreign key value to null in related records
- SET DEFAULT: sets foreign key value to its default in related records
- NO ACTION/RESTRICT: prevents changes if related records exist
36
Pros and cons of referential integrity
- Pros: ensures data consistency and accuracy, prevents orphaned records
- Cons: can impact performance due to additional checks, may require additional planning and design
37
What is a transaction?
- A sequence of database operations treated as one single unit of work
38
What is the aim of transaction processing?
- Ensure data consistency and integrity during simultaneous access
39
What problems arise from transaction processing?
- Concurrency: when multiple transactions occur at the same time, they might try to access the same piece of data, leading to inconsistencies
- Deadlock: when two or more transactions are waiting for resources that the other is using
- Data integrity: transactions may leave the database in an inconsistent state if they fail mid-execution
- Isolation: one user's transaction may affect another user's transaction, leading to unpredictable problems
- Durability: if a system fails after a transaction has been confirmed, it may lead to a loss of data
40
What are the solutions to overcome the problems that arise from transaction processing?
- Locking: no two transactions can access the same data simultaneously; shared locks and exclusive locks
- Deadlock prevention: ordering the way in which resources are requested
- Logging and recovery: system can recover to a consistent state after a crash
- Commit and rollback: the commit operation saves all changes made in a transaction. The rollback operation reverts the changes made
- Two-phase commit protocol
- Concurrency control
- Transaction management
41
What is the two-phase commit protocol?
- In distributed systems, this protocol ensures that a transaction is completed in all participating nodes, or none at all, to maintain consistency
42
What is the concurrency control?
- Manages simultaneous access to data in a multi-user environment
- The two methods are locking and time-stamping
- Locking: prevents multiple transactions from accessing the same data simultaneously
- Time-stamping: assigns a unique timestamp to each transaction
43
What is transaction management?
- Uses database management systems (DBMS) with built-in transaction support
- Implement custom transaction logic using SQL or other query languages
- Test and monitor transactions to ensure ACID compliance and performance
44
What is ACID and what is its aim?
- A set of rules that database management systems (DBMS) must use to ensure data integrity
- Stands for Atomicity, Consistency, Isolation and Durability
- It guarantees reliable processing of transactions
45
What is atomicity in ACID?
- All operations in a transaction will succeed or fail as a whole
- If any operation fails, the transaction is rolled back
- Ensures partial transactions do not occur
46
What is consistency in ACID?
- Ensures data remains in a consistent state after a transaction
- Transactions must follow database rules and constraints
- Starts and ends with a consistent state
47
What is isolation in ACID?
- Transactions are isolated from eachother
- Immediate states are not visible to other transactions
- Prevents conflict and data inconsistencies
48
What is durability in ACID?
- Committed transactions persist even in case of system failure
- Ensures data is not lost once a transaction is complete
49
What is record locking?
- A technique used in database management systems (DBMS) to prevent conflicting access to data by multiple transactions
- It ensures data consistency and integrity when multiple users or processes try to read, modify or delete records simultaneously
50
What are the key concepts of record locking?
- Lock: a mechanism that prevents access to a database record while a specific transaction is using the record
- Lock granularity: refers to the size of the locked data, ranging from a single row to an entire table
51
What are the types of record locks?
- Shared lock: allows multiple transactions to read a record simultaneously, but prevents modifications or deletions until the record is released
- Exclusive lock: allows only one transaction to read and modify a record, blocking other transactions until it is released
52
What are the benefits of record locking?
- Maintains data consistency and integrity by preventing conflicting modifications
- Allows concurrent read access to records without compromising data consistency
53
What is data redundancy?
- Can occur when the same piece of data is stored in more than one table in the same database
- It can lead to inconsistencies in the data and/or wasted storage
Computer Science A-Level
flashcards
Decks in class (17)
# Cards
-
Systems Software19
-
Computational thinking14
-
Applications generation23
-
Characteristics of the CPU54
-
Data types24
-
Web technologies30
-
Object Orientated Programming21
-
Boolean logic22
-
Algorithms40
-
Types of programming languages17
-
Ethics and legislations15
-
Software development22
-
Compression, encryption and hashing18
-
Databases53
-
Problem solving and programming46
-
Networks92
-
Data structures45
