1. What is a Data Warehouse?
A Data Warehouse is a collection of data marts representing historical data from different operational data source (OLTP). The data from these OLTP are structured and optimized for querying and data analysis in a Data Warehouse.
2. What is a Data mart?
A Data Mart is a subset of a data warehouse that can provide data for reporting and analysis on a section, unit or a department like Sales Dept, HR Dept, etc. The Data Mart are sometimes also called as HPQS (Higher Performance Query Structure).
3. What is OLAP?
OLAP stands for Online Analytical Processing. It uses database tables (Fact and Dimension tables) to enable multidimensional viewing, analysis and querying of large amount of data.
4. What is OLTP?
OLTP stands for Online Transaction Processing Except data warehouse databases the other databases are OLTPs. These OLTP uses normalized schema structure. These OLTP databases are designed for recording the daily operations and transactions of a business.
5. What are Dimensions?
Dimensions are categories by which summarized data can be viewed. For example a profit Fact table can be viewed by a time dimension.
6. What are Confirmed Dimensions?
The Dimensions which are reusable and fixed in nature Example customer, time, geography dimensions.
7. What are Fact Tables?
A Fact Table is a table that contains summarized numerical (facts) and historical data. This Fact Table has a foreign key-primary key relation with a dimension table. The Fact Table maintains the information in 3rd normal form.
A star schema is defined is defined as a logical database design in which there will be a centrally located fact table which is surrounded by at least one or more dimension tables. This design is best suited for Data Warehouse or Data Mart.
8. What are the types of Facts?
The types of Facts are as follows.
1. Additive Facts: A Fact which can be summed up for any of the dimension available in the fact table.
2. Semi-Additive Facts: A Fact which can be summed up to a few dimensions and not for all dimensions available in the fact table.
3. Non-Additive Fact: A Fact which cannot be summed up for any of the dimensions available in the fact table.
9. What are the types of Fact Tables?
The types of Fact Tables are:
1. Cumulative Fact Table: This type of fact tables generally describes what was happened over the period of time. They contain additive facts.
2. Snapshot Fact Table: This type of fact table deals with the particular period of time. They contain non-additive and semi-additive facts.
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