Common Warehouse Interview Questions to read before your next interview
Data Warehousing and Business Intelligence (DWBI) is a rewarding career choice if you love managing data. And If you are looking for your next job in Data Warehouse, here are some of the most common Data Warehouse interview questions.
1. What is Data Warehouse?
A Data Warehouse is the automated storage of an organization’s historical data to help with data analytics. The data reinforces the decision-making process in a company.
2. List the Data Warehouse Architectures.
There are 3 types of data warehouse architectures.
a) Single Tier Architecture - The aim of a single layer is to reduce the amount of stored data by clearing redundant data.
It is not normally used.
b) Two Tier Architecture - This architecture separates physically accessible sources from the warehouse.
- This architecture cannot be expanded, and it does not support a large number of end-users.
- This architecture faces connectivity issues due to network restrictions.
c) Three Tier Architecture - This is the most popular architecture. It is made up of the Bottom, Middle and Top Tier.
- Bottom Tier – This is an interactive database of the Data Warehouse. The data is transformed, cleansed and loaded.
- Middle Tier – This is an OLAP server. It gives a hypothesized view of the database which serves as a mediator between the database and end-user.
- Top Tier – This is a front-end client layer and directs data out of the Data Warehouse.
3. Explain Data Analytics in the context of Data Warehousing.
• Data analytics is the discipline of studying new data for the intention of drawing business-driven deductions from the data.
• The purpose of a Data Warehouse is to allow data analysis.
4. Explain Subject-Oriented Data Warehouse.
Subject-oriented data warehouses are those that keep data around a certain subject such as sales, product and customers among others.
What is OLAP?
OLAP is On Line Analytical Processing. It is a system which collects, processes and manages multi-dimensional data for management and analysis.
5. What is OLTP?
OLTP is On Line Transaction Processing. It is a system which adapts the data when it is received by a large number of current users.
6. What are the Types of OLAP Servers?
• Multidimensional OLAP.
• Relational OLAP.
• Specialized SQL Servers.
• Hybrid OLAP.
7. What are Some of the Functions Carried Out by OLAP?
Some of the major functions carried out by OLAP include pivot, dice, slice, drill-down and roll-up.
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8. What is a Star Schema?
The star schema is a representation used in data warehousing when a single fact table notes a range of dimension tables. For a star schema ‘keys’ from all the dimension tables move into the fact table. This entity-relationship diagram looks like a star giving it its name.
9. What is a Snow Flake Schema?
Like the star schema a single fact table refers to a number of other dimension tables in the snow flake schema. These dimension tables are additionally standardised into numerous related tables. This schema is called a snowflake schema as the tables are snow flaked into smaller tables further.
10. What do you understand by a Mini Dimension?
Mini dimensions are measurements that are used when a large number of promptly changing attributes are separated.
11. What is ER Model?
The ER Model or Entity Relations Model is a method for data modelling where the goal is to regularise the data by reducing redundancy.
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