07-1-Definitions-to-learn
Definitions or Pre Test Notes
Data Warehouse
A data warehouse is a separate relational database from the OLTP relational database that runs your day-to-day
operations. The purpose is to provide business analysis ability to the company in a timely and meaningful
manner that is not easily available from the OLTP system and the queries do no degrade the performance of the
OLTP system. The data from the OLTP is used in the DW as well as other sources of data.
Fact Table
The Fact table is a very large table that holds keys and measures. The measures provide numerical analysis and
the keys connect to dimension tables to provide the context or restrictions or textual description for analysis.
Dimension Table
A table that connects to a fact table by keys is called a dimension table. The dimension table contains
descriptive text data for analysis purposes. Example Product name connects via product key to the fact table and
through the keys to other dimension tables. Such analysis as Dales by month for a product is possible.
Dimension tables answer the who, what where questions.
Data Storage Methods
- & advantages or disadvantages
ROLAP
MOLAP
HOLAP
Measures
Types of Measures
1
2
Additive
Semi-additive
Non-additive
Continuously valued
OLAP - Online Analytical Processing
- Software that allows users to easily analyse data online by manipulating the presentation of facts
and dimensions.
- By now you have seen a little of it
OLTP - Online Transaction Processing
- Software that processes business transactions such as order processing, visitor registration, support
calls
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Facts
- Numeric values that represent
- Amounts
- Sales $
- Amt
- Quantity on Hand)
- Or events
- Registration count
Dimensions
- Hierarchies that represent the perspectives a business can take of the facts
- Time
- Product
- Geography
- Customer
RDBMS - Relational Database Management System
- Software for building and managing databases using SQL (Standard Query Language)
Data Mart
- A targeted subset of a data warehouse to support a particular subject area or departmental
requirement
Cube
- A multidimensional database (MDDB) pre-summarized (aggregation) for fast performance and easy
slice-and-dice
Slice-and-Dice
- The action of changing dimensions to see information from a different perspective
ROLL-UP
- Aggregate on some dimension
- Daily aggregates into weekly, monthly etc
- Store data aggregates into stores in city, region, province, and country
DRILL-DOWN
- De-aggregate on some dimension
- Getting at greater levels of detail
CLIENTS
- Query and reporting tools
- Analysis tools
DATA MINING
- Discovering patterns of various forms by “mining” through the data
- Client tools used to do mining
- PowerPlay
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E.T.L.
Slowly Changing Dimensions
How to solve – 3 ways
Advantages and Disadvantages
Surrogate Keys
Advantage
STAR SCHEMA
SNOWFLAKE SCEMA
Advantages and Disadvantages
Example
OLTP vs OLAP
Example
Factless Table
Example
Draw a visual of the Overall process from OLTP to Executive
Grain
Partitions
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