In the dynamic realm of data analytics, companies like RBHU Analytics are constantly seeking top-tier talent to harness the power of data for informed decision-making. Aspiring candidates aiming to make their mark in the data analytics field must be well-prepared for the rigorous interview process. One crucial aspect of these interviews is the evaluation of proficiency in SQL, the cornerstone of database management and analytics. In this blog, we will delve into key data analytics and SQL interview questions, providing comprehensive answers to help you ace your interview at RBHU Analytics.
Table of Contents
Power BI Interview Questions
Question: What is Power BI?
Answer: Power BI is a business analytics tool developed by Microsoft. It allows users to visualize and analyze data, create interactive reports, and share insights across an organization. Power BI connects to various data sources and provides a unified view of data through customizable dashboards.
Question: Explain the difference between Power BI Desktop and Power BI Service.
Answer: Power BI Desktop is a desktop application for creating reports and dashboards, while Power BI Service is a cloud-based platform for publishing, sharing, and collaborating on Power BI content. Power BI Desktop is used for authoring reports, and Power BI Service is used for sharing and consuming those reports.
Question: How does Power BI handle data refresh and scheduling?
Answer: Power BI supports scheduled data refresh for datasets hosted in Power BI Service. It allows users to configure automatic refreshes from various data sources, ensuring that the data in the Power BI reports is up-to-date. The refresh frequency depends on the user’s subscription or the workspace settings in Power BI Service.
Question: What are the different components of a Power BI report?
Answer: A Power BI report consists of visualizations (charts, tables, etc.), pages, filters, and datasets. Visualizations represent the graphical elements, pages organize content, filters control data visibility, and datasets contain the data used in the report.
Question: Explain the role of Power Query in Power BI.
Answer: Power Query is a data connection technology in Power BI used for transforming and shaping data from various sources before it is loaded into the data model. Power Query provides a visual interface for data cleaning, transformation, and merging operations.
Question: What is DAX (Data Analysis Expressions) in Power BI?
Answer: DAX is a formula language used for creating custom calculations and aggregations in Power BI. It allows users to define custom measures, columns, and tables based on the data in the Power BI model.
SQL Interview Questions
Question: Explain the difference between INNER JOIN and LEFT JOIN in SQL.
Answer: INNER JOIN returns only the matching rows from both tables, while LEFT JOIN returns all rows from the left table and the matching rows from the right table. If there is no match, NULL values are returned for columns from the right table.
Question: What is a subquery in SQL?
Answer: A subquery is a query nested within another query. It can be used to retrieve data that will be used in the main query as a condition to further restrict the data to be retrieved.
Question: How do you handle duplicate records in a SQL query result?
Answer: To handle duplicate records, you can use the DISTINCT keyword in the SELECT statement or apply the GROUP BY clause along with aggregate functions to consolidate data.
Question: Explain the difference between UNION and UNION ALL in SQL.
Answer: UNION removes duplicate rows from the combined result set, while UNION ALL includes all rows, including duplicates.
Question: What is the purpose of the HAVING clause in SQL?
Answer: The HAVING clause is used in conjunction with the GROUP BY clause to filter the results of a GROUP BY based on specified conditions. It is applied after the grouping and aggregation.
Question: What is the importance of indexes in a database?
Answer: Indexes improve the speed of data retrieval operations by providing a quick way to locate and access rows in a database table. They enhance query performance and reduce the time needed to retrieve data.
SQL Query Basics
Question: What is SQL?
Answer: SQL (Structured Query Language) is a standard language for managing and manipulating relational databases. It is used for tasks such as querying data, updating data, and defining and managing database schemas.
Question: Differentiate between SQL and NoSQL databases.
Answer: SQL databases are relational and use a structured schema, while NoSQL databases are non-relational and do not require a fixed schema. SQL databases use SQL for querying, NoSQL databases use various query languages.
- SELECT Statement:
Question: Explain the basic structure of a SELECT statement.
Answer: The basic structure of a SELECT statement is:
SELECT column1, column2, … FROM table WHERE condition;
Question: How do you retrieve all columns from a table named “employees”?
Answer: Use the asterisk (*) wildcard:
SELECT * FROM employees;
WHERE Clause and Filtering:
Question: What is the purpose of the WHERE clause in a SQL query?
Answer: The WHERE clause filters rows based on specified conditions, allowing you to retrieve only the data that meets certain criteria.
Question: How do you retrieve records where the “salary” column is greater than 50000 in the “employees” table?
Answer:
SELECT * FROM employees WHERE salary > 50000;
SQL Joins Questions
Question: Explain the INNER JOIN in SQL.
Answer: INNER JOIN retrieves records from two or more tables based on a related column, excluding rows where there is no match between the tables.
Question: Provide an example of using an INNER JOIN to retrieve data from two tables.
Answer:
SELECT employees.employee_id, employees.employee_name, departments.department_name
FROM employees
INNER JOIN departments
ON employees.department_id = departments.department_id;
Aggregation Functions:
Question: What is the purpose of the COUNT() function in SQL?
Answer: COUNT() is an aggregate function that counts the number of rows in a result set.
Question: How do you retrieve the total number of employees in the “employees” table?
Answer:
SELECT COUNT(*) FROM employees;
Group By and Having Clause:
Question: Explain the GROUP BY clause in SQL.
Answer: GROUP BY is used to group rows that have the same values in specified columns into summary rows.
Question: Provide an example of using GROUP BY and HAVING to find departments with more than 10 employees.
Answer:
SELECT department_id, COUNT(*) as employee_count
FROM employees
GROUP BY department_id HAVING COUNT(*) > 10;
Other Questions
Question: What is server?
Answer: In the context of cloud computing, a server usually refers to a virtualized computing instance that runs on a physical server within a cloud infrastructure. Cloud servers provide scalable and flexible computing resources, and users can provision or de-provision them as needed. Cloud servers are a fundamental building block in Infrastructure as a Service (IaaS) offerings.
Question: What is ETL?
Answer: ETL stands for Extract, Transform, Load, and it refers to a process in data integration where data is extracted from source systems, transformed into a desired format, and loaded into a target data repository or data warehouse. ETL is a crucial step in preparing and consolidating data for analysis, reporting, and business intelligence purposes.
Question: What is an SQL Database
Answer: In the context of information technology and databases, an SQL database refers to a relational database management system (RDBMS) that uses the Structured Query Language (SQL) for managing and manipulating data. SQL databases are based on the relational model, which organizes data into tables with rows and columns, and they use SQL for querying and interacting with the data.
Question: What is data warehousing?
Data warehousing is a centralized repository that integrates and stores large volumes of structured and historical data from diverse sources. It provides a subject-oriented structure, focusing on key business areas for comprehensive reporting and analytics. Utilizing ETL processes ensures data quality and consistency. Data warehouses are optimized for analytical processing, supporting OLAP for multidimensional analysis. They serve as the backbone for Decision Support Systems and Business Intelligence, enabling informed decision-making. Popular technologies include Amazon Redshift, Azure Synapse Analytics, and Google BigQuery.
Question: What is server cloud computing?
A server in cloud computing refers to a virtualized computing instance running on a physical server within a cloud infrastructure. These instances are created through virtualization, allowing efficient resource utilization. Cloud servers offer on-demand resources and scalability, allowing users to adjust computing power based on workload fluctuations. Following a pay-as-you-go model, users are charged for consumed resources. Managed services, global accessibility, and various configurations make cloud servers a key component of Infrastructure as a Service (IaaS) provided by platforms like AWS, Azure, and Google Cloud.
Question: What is Primary Key?
Answer: In SQL, a Primary Key is a field or combination of fields in a table that uniquely identifies each row. It ensures the uniqueness and non-null status of values, playing a crucial role in maintaining entity integrity. Primary keys can be single or composite, and they are often automatically indexed for improved query performance. Declared using the PRIMARY KEY constraint during table creation, primary keys are essential for establishing relationships between tables and enforcing referential integrity. Auto-incrementing primary keys, commonly used for surrogate keys, automatically generate unique values for each new record.
Question: What are triggers and types of trigger?
Answer: In SQL, a trigger is a set of instructions or code that automatically executes in response to specific events on a table or view. There are two main types of triggers:
- DML Triggers (Data Manipulation Language Triggers):
These triggers respond to INSERT, UPDATE, or DELETE operations on a table. They can be categorized as BEFORE triggers (executed before the event) or AFTER triggers (executed after the event).
- DDL Triggers (Data Definition Language Triggers):
DDL triggers respond to changes in the database schema, such as CREATE, ALTER, or DROP operations on tables, views, or other database objects.
Question: SQL windows function.
Answer: In SQL, a window function (or analytic function) is a type of function that performs a calculation across a specified range of rows related to the current row within the result set. These functions operate on a “window” of rows defined by an OVER() clause, allowing for advanced analytical and statistical operations without the need for self-joins or subqueries.
Question: what is cloud computing?
Answer: Cloud computing refers to the delivery of computing services, including computing power, storage, databases, networking, analytics, software, and more, over the internet (the cloud) to offer faster innovation, flexible resources, and cost savings. Instead of owning and maintaining physical hardware and infrastructure, users can access and utilize computing resources on a pay-as-you-go basis from a cloud service provider.
Question: What are functions in SQL?
Answer:
Definition:
Functions in a database are reusable blocks of code that perform a specific operation and return a single value or a table. They can be user-defined or system-defined.
Use Cases:
Functions are primarily used to encapsulate and modularize logic, making it easier to manage and reuse. They can be employed in SELECT statements, WHERE clauses, or within other stored procedures and functions.
Types:
SQL databases support various types of functions, including:
- Scalar Functions: Return a single value.
- Table-Valued Functions: Return a table as the result.
- Aggregate Functions: Perform a calculation on a set of values and return a single value.
Example:
An example of a user-defined function could be a function that calculates the total salary of employees in a specific department.
Conclusion:
In conclusion, mastering data analytics and SQL is pivotal for success in interviews, particularly with esteemed companies like RBHU Analytics. A solid grasp of fundamental SQL concepts, data retrieval, joins, aggregate functions, and data modification is essential. By diligently preparing the provided questions and answers, you’ll not only showcase your expertise but also position yourself as a valuable asset to RBHU Analytics. Best of luck in your interview journey – may your skills shine brightly, and your data analytics career soar to new heights!
