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Big Data - AQA Computer Science Cheat Sheet
This is a draft cheat sheet. It is a work in progress and is not finished yet.
5 Vs of Big Data
Variety |
The range of data formats and data types collected |
Value |
How useful data is to an organisation |
Veracity |
Accuracy and quality of data |
Volume |
The amount of data (if the volume is large enough, it is considered big data) |
Velocity |
How quickly the data is generated |
Example Big Data Applications
Healthcare |
Predict disease outbreaks and personalize treatment plans |
Entertainment |
Recommend content and analyze audience preferences |
Transportation |
Improve traffic flow and predict maintenance needs |
Retail |
Optimize inventory and personalize customer recommendations |
Finance |
Detect fraudulent transactions in real-time |
Relationships in Relational Databases
One-to-one |
One school has one principle |
One-to-many |
One school has many students |
Many-to-many |
Many students and take many subjects |
Entity Relationship Diagram
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Relational Databases
Table |
Set of facts or figures that are set out in a column and row structure |
Flat-file database |
Database that stores all data items using one table |
Data redundancy |
When data is unnecessarily repeated in a database |
Data-entry error |
Error that occurs when data is being entered into a database |
Relational database |
Database that stores data using two or more linked tables |
Entity |
Person, place or object represented in a table in a relational database |
Attribute |
Heading for organising data in a relational database |
Primary key |
Field in a database table that provides a unique identifier for a record/entity |
Foreign key |
When the primary key from one table appears in another table to establish a link between two entities |
Query
Simple queries |
Only a single search criterion is used to select data items from a database |
Complex queries |
More than one criterion is used to search a database, a query is used to combine data from more than one table, or calculations are performed using the data in a query or a report |
Parameter queries |
Queries where the end user provides the search criteria |
Wildcard queries |
Queries where special characters are used to stand in for unknown characters (this is useful when trying to find lots of data items that are similar but not exactly the same) |
Multi-table queries |
Use data from more than one data table |
Multiple-criteria queries |
Use more than one criterion to select data items from a database |
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Spreadsheet Model
Function |
Sub-program that can exist as part of a bigger program |
MIN function |
Returns the lowest value in a specified range of cells in a spreadsheet |
MAX function |
Returns the highest value in a specified range of cells in a spreadsheet |
IF statement |
This evaluates a condition which determines the path of the program depending on whether the condition is true or false |
COUNT function |
Checks all the cells in a specified range in a spreadsheet and outputs how many contain a numeric value |
Evaluating models
Evaluation: checking the suitability of a solution to a problem |
Efficient: the efficiency of a program can be measured by how quickly it runs |
User requirements: tasks a user expects of an application |
Data type: classification applied to a data item specifying which type of data that item represents, e.g. in a spreadsheet some of the data types available include currency, text and number |
Frameworks
Structured Query Language (SQL) |
Specialised language for accessing data in relational databases |
Query by Example (QBE) |
Interface that allows users to select fields and criteria for use in a query in a database application |
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