# OLAP

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“OLAP Interview Questions and Answers will guide us now that Online analytical processing (OLAP) is an approach to quickly answer multi-dimensional analytical queries. OLAP is part of the broader category of business intelligence, which also encompasses relational reporting and data mining. So learn OLAP or get preparation for a job of OLAP with the help of this OLAP Interview Questions with Answers guide”

## 47 OLAP Questions And Answers

### 1⟩ Explain about the role of bitmap indexes to solve aggregation problems?

Bitmaps are very useful in start schema to join large databases to small databases. Answer queries and bit arrays are used to perform logical operations on the databases. Bit map indexes are very efficient in handling Gender differentiation; also repetitive tasks are performed with much larger efficiency.

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### 2⟩ Explain about Encoding technique used in bitmaps indexes?

Bitmaps commonly use one bitmap for every single distinct value. Number of bitmaps used can be reduced by opting for a different type of encoding. Space can be optimized but when a query is generated bitmaps have to be accessed.

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### 3⟩ Explain about the view selection problem?

Often calculating all the data is not possible by aggregations for this reason some of the complex data problems are solved. In order to determine which data should be solved and calculated, developers use View selection application. This solution is often used to reduce calculation problem.

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OLAP can process complex queries and give the output in less than 0.1 seconds, for it to achieve such a performance OLAP uses aggregations. Aggregations are built by aggregating and changing the data along the dimensions. Possible combination of aggregations can be determined by the combination possibilities of dimension granularities.

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### 5⟩ What is ROLAP?

Functioning of ROLAP occurs simultaneously with relational databases. Data and tables are stored as relational tables. To hold new information or data new tables are created. Functioning of ROLAP depends upon specialized schema design.

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Classic form of OLAP is known as MOLAP and it is often called as OLAP. Simple database structures such as time period, product, location, etc are used. Functioning of each and every dimension or data structure is defined by one or more hierarchies.

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### 7⟩ Explain about the functionality of OLAP?

Hyper cube or multidimensional cube forms the core of OLAP system. This consists of measures which are arranged according to dimensions. Hyper cube Meta data is created by star or snow flake schema of tables in RDBMS. Dimensions are extracted from dimension table and measures from the fact table.

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OLAP is known as online analytical processing which provides answers to queries which are multi dimensional in nature. It composes relational reporting and data mining for providing solutions to business intelligence. This term OLAP is created from the term OLTP.

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### 9⟩ What is sparsity? a) A condition when each cell of the cube is filled with data and that leads to more processing time. b) A condition when each cell of the cube is not filled with data and that leads to less processing time. c) A condition when each cell of the cube is not filled with data and that leads to more processing time. d) A condition when each cell of the cube is not filled with data.

a) A condition when each cell of the cube is filled with data and that leads to more processing time.

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d) Both 1 and 2

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### 11⟩ What is OLAP?

OLAP is an acronym for Online Analytical Processing. OLAP performs multidimensional analysis of business data and provides the capability for complex calculations, trend analysis, and sophisticated data modeling.

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### 12⟩ What are Cubes in OLAP?

A data cube stores data in a summarized version which helps in a faster analysis of data. The data is stored in such a way that it allows reporting easily. E.g. using a data cube a user may want to analyze weekly, monthly performance of an employee. Here, month and week could be considered as the dimensions of the cube.

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### 13⟩ What are Database roles in OLAP?

Database level roles are used to manage the security of the database. The role can be either fixed or flexible. Fixed roles are predefined while flexible roles can be created. Examples of some fixed database level roles are db_owner, db_securityadmin, db_datawriter etc.

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### 14⟩ Select item name, color, clothes size, sum(quantity) from sales group by rollup(item name, color, clothes size); How many grouping is possible in this rollup? a) 8 b) 4 c) 2 d) 1

b) 4

Explanation:

{ (item name, color, clothes size), (item name, color), (item name), () }.

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### 15⟩ Where is Data Sources in OLAP?

Data source is where the data comes from in data warehousing. The data collected from various sources and is cleaned. The data source can be internal or external. Efficient Analysis and cleansing of source data is the key success to data warehousing.

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### 16⟩ What are Fact Tables?

Data in a warehouse comes from the transactions. Fact table in a data warehouse consists of facts and/or measures. The nature of data in a fact table is usually numerical. e.g. If I want to know the number of resources used for a task, my fact table will store the actual measure (of resources) while my Dimension table will store the task and resource details.

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### 17⟩ Which one of the following is the right syntax for DECODE ? a) DECODE (search, expression, result [, search, result]… [, default]) b) DECODE (expression, result [, search, result]… [, default], search) c) DECODE (search, result [, search, result]… [, default], expression) d) DECODE (expression, search, result [, search, result]… [, default])

d) DECODE (expression, search, result [, search, result]… [, default])

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### 18⟩ Which of the following below is/are OLAP vendors? a) Cognos b) Infor c) Oracle corporation d) All of the above

d) All of the above

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### 19⟩ Data that can be modeled as dimension attributes and measure attributes are called _______ data. a) Multidimensional b) Singledimensional c) Measured d) Dimensional

a) Multidimensional

Explanation:

Given a relation used for data analysis, we can identify some of its attributes as measure attributes, since they measure some value, and can be aggregated upon.Dimension attribute define the dimensions on which measure attributes, and summaries of measure attributes, are viewed.

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### 20⟩ Explain about the database marketing application of OLAP?

Database marketing tool or application helps a user or marketing professional in determining the right tool or strategy for his valuable add campaign. This tool collects data from all sources and gives relevant information the specialist with their add campaign. It gives a complete picture to the developer.

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