A guide to Data Analyst Interview Questions and Answers at Wipro

February 12, 2024

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Aspiring to become a data analyst at Wipro? Congratulations on taking the first step towards a rewarding career in data analytics! Landing a job as a data analyst at Wipro requires not only strong technical skills but also the ability to effectively communicate your knowledge and problem-solving abilities during the interview process. In this blog post, we’ll explore some common data analyst interview questions you may encounter at Wipro, along with detailed answers to help you prepare and ace your interview.

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Technical questions on SQL and Power BI

Question: What is SQL?

Answer: SQL (Structured Query Language) is a domain-specific language used for managing and manipulating relational databases. It allows users to query, insert, update, and delete data from databases.

Question: What are the different types of SQL joins?

Answer: SQL supports various types of joins, including INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN. These joins are used to combine rows from multiple tables based on specified conditions.

Question: What is normalization in SQL?

Answer: Normalization is the process of organizing data in a database to reduce redundancy and dependency. It involves dividing large tables into smaller tables and defining relationships between them to ensure data integrity.

Question: What is a subquery in SQL?

Answer: A subquery is a query nested within another query. It can be used to retrieve data from one or more tables based on specific conditions and then use that result set as a part of the main query.

Question: Explain the difference between GROUP BY and ORDER BY in SQL.

Answer: GROUP BY is used to group rows that have the same values into summary rows, typically used with aggregate functions like SUM, COUNT, AVG. ORDER BY, on the other hand, is used to sort the result set either in ascending (ASC) or descending (DESC) order based on specified columns.

Question: What is Power BI?

Answer: Power BI is a business analytics tool by Microsoft used for creating interactive visualizations and reports from various data sources. It enables users to analyze data, share insights, and make data-driven decisions.

Question: What are the different components of Power BI?

Answer: Power BI consists of Power BI Desktop, Power BI Service (cloud-based service), and Power BI Mobile (mobile application). Power BI Desktop is used for creating reports and visualizations, while Power BI Service allows sharing and collaboration on reports.

Question: How do you import data into Power BI?

Answer: Data can be imported into Power BI from various sources such as Excel files, databases (SQL Server, MySQL, etc.), Azure services, web sources, and more. In Power BI Desktop, users can use the “Get Data” option to connect to and import data from these sources.

Question: What is a Power BI dashboard?

Answer: A Power BI dashboard is a single-page canvas that uses visualizations to tell a story from data. It provides a consolidated view of key metrics and insights, allowing users to monitor the health of their business and make data-driven decisions.

Other data analytics questions

Question: Explain the difference between calculated columns and measures in Power BI.

Answer: Calculated columns are columns added to a table in Power BI, calculated based on a formula applied to each row in the table. Measures, on the other hand, are calculated values based on aggregations or calculations performed on data in the dataset, typically used in visualizations.

Question: What is the difference between inner and outer join in SQL

Answer: The difference between INNER JOIN and OUTER JOIN in SQL lies in how they handle unmatched rows:

INNER JOIN:

Returns only the rows that have matching values in both tables based on the specified join condition.

Essentially forms the intersection of the two tables.

Excludes rows where there is no match between the columns being compared.

OUTER JOIN:

Includes all rows from one or both tables, even if there are no matches.

Unmatched rows are represented by NULL values in the columns from the table lacking a match.

Further categorized into LEFT, RIGHT, and FULL OUTER JOIN, each with specific behaviors regarding unmatched rows.

Question: What is meant by V lookup and what are the limitations?

Answer: VLOOKUP, short for Vertical Lookup, is a function in spreadsheet software like Excel. It searches for a value in the first column of a table and returns a corresponding value from a specified column. It takes four arguments: the value to search for, the table range, the column number to retrieve the value from, and an optional flag for exact or approximate matching. VLOOKUP is commonly used for quick data retrieval within large datasets.Limitations of VLOOKUP:

Searches only in the first column of the table array.
Requires data to be sorted for approximate matches.
Retrieves data only from columns to the right of the lookup column.
Column indices are static and need manual updating if the table structure changes.
Performance may degrade in large datasets and it’s not case-sensitive.

Question: What does distinct do in SQL?

Answer: In SQL, the DISTINCT keyword is used to retrieve unique values from a specified column or columns in a query result. When used, it eliminates duplicate rows from the result set, ensuring that each row returned is distinct. This can be particularly useful when querying data from tables containing redundant or duplicated information, allowing you to focus on unique values.

Question: What is the difference between foreign and primary keys in SQL?

Answer:

Primary Key:

Uniquely identifies each row in a table.

Must contain unique values and cannot be NULL.

Only one primary key constraint is allowed per table.

Ensures data integrity by enforcing uniqueness and serving as a reference for relationships with other tables.

Foreign Key:

Refers to the primary key in another table.

Establishes relationships between tables, forming parent-child connections.

Ensures referential integrity by requiring values in the foreign key column(s) to match those in the primary key column(s) of the referenced table.

Multiple foreign key constraints can exist in a table, allowing relationships with multiple parent tables.

Question: What does order is used for in SQL.

Answer: In SQL, the ORDER BY clause is used to sort the result set of a query based on one or more columns. It arranges the rows returned by a SELECT statement in either ascending (ASC) or descending (DESC) order. ORDER BY is particularly useful when you want to view data in a specific sequence, such as alphabetical order for names or numerical order for values.

Question: What are the types of loops used in programming?

Answer: In programming, there are several types of loops used for iterating over a block of code repeatedly until a certain condition is met:

For Loop: A for loop iterates over a specific range of values or elements in a collection. It typically consists of an initialization, a condition, and an increment or decrement operation.
While Loop: A while loop repeatedly executes a block of code as long as a specified condition evaluates to true. It’s used when the number of iterations is not known beforehand.
Do-While Loop: Similar to a while loop, a do-while loop executes a block of code at least once before checking the condition for subsequent iterations. It’s useful when you want to ensure that the block of code runs at least once.
For Each Loop (or Enhanced For Loop): This type of loop is used for iterating over elements in an array or collection without explicitly using an index variable. It’s commonly used in languages that support iterable objects.

Question: What is the difference between For loop and while loop?

Answer: The difference between a for loop and a while loop lies in their syntax and usage:

For Loop:

Has a specific syntax with an initialization, condition, and increment/decrement operation all in one line.

Ideal for iterating over a fixed range of values or elements in a collection where the number of iterations is known.

Provides a concise and structured way to control the loop execution.

While Loop:

Has a simpler syntax with just a condition to check before each iteration.

Continues iterating as long as the specified condition evaluates to true, making it suitable for scenarios with uncertain iteration counts or complex termination conditions.

Offers more flexibility in loop control but requires explicit initialization and update of loop variables inside the loop body.

Question: What is Data Science?

Answer: Data Science is an interdisciplinary field that uses scientific methods, algorithms, and technologies to analyze and extract insights from data. It combines aspects of mathematics, statistics, computer science, and domain expertise to uncover patterns, trends, and correlations in data sets. The goal is to derive actionable insights and solutions to complex problems across various industries.

List the differences between supervised and unsupervised learning.

Definition: Supervised learning involves training a model on labeled data to predict output labels, while unsupervised learning deals with unlabeled data to discover patterns.
Input Data: Supervised learning requires labeled datasets where each input has a corresponding output label, whereas unsupervised learning uses unlabeled data without predefined output labels.
Goal: Supervised learning aims to predict or classify new data based on learned patterns, while unsupervised learning seeks to explore hidden structures or relationships within the data.
Algorithms: Supervised learning employs regression, classification, and neural networks trained on labeled data, whereas unsupervised learning utilizes clustering, dimensionality reduction, and association algorithms on unlabeled data.
Evaluation: Supervised learning models are evaluated based on predictive accuracy using metrics like accuracy, precision, or recall, while unsupervised learning models are assessed on the quality and meaningfulness of discovered patterns or clusters.
Application: Supervised learning is commonly used in tasks like spam detection, image recognition, and sentiment analysis, while unsupervised learning finds applications in customer segmentation, anomaly detection, and data compression.