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Q:

Difference between ER Modeling and Dimensional Modeling. 

Answer:



Q:

Define "Correlated Subqueries" ?

Answer

In a SQL Database, a 'correlated subquery' is a kind of sub query yet connected subquery is dependent on another query for a value that is returned. In case of execution, the sub query is executed first and afterwards the correlated query will be executed.

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Q:

Define what is a Fact, Dimension and Measure ?

Answer

Fact is key performance indicator to analyze the business.From the additive values, which are used to analyse the business by using report generation. Dimension is used to analyze the fact, are the non-additive ( text format) values, Which are used to drill down reports.Without dimension there is no meaning for fact. Measure is the quantity of data we create to process.

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Q:

What does BUS Schema means ?

Answer

BUS Schema is composed of a master suite of confirmed dimension and standardized definition if facts.

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Q:

State the difference between View and Materialized View ?

Answer

The main differenc between View and Materialized View states that -


1. View means it stores the SQL statement in the database and let you use it as a table. Everytime you access the view, the SQL statement executes.


2. Materialized view means it stores the results of the SQL in table form in the database. SQL statement only executes once and after that everytime you run the query, the stored result set is used. Advantage include quick query results.

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Q:

What is the difference between operational data stage (ODS) and data warehouse?

Answer

Data warehouse


- It is a decision support database system for the purpose of organizational needs. 


-It is non volatile, integrated and time variant collection of data


 


Operational Data Stage


- It is an integrated collection of information. 


-It can contain 90 days of information at maximum.


-ODS supports dynamic data.

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