100+ Junior Data Analyst Interview Questions and Answers

Data mining involves discovering patterns and relationships in large datasets, while data analysis focuses on interpreting and drawing insights from data.

• Data mining is the process of extracting useful information from large datasets.

• Data analysis involves examining and interpreting data to draw conclusions and make informed decisions.

• Data mining uses techniques like clustering, classification, and association to discover patterns and relationships.

• Data analysis involves tech...read more

PARTITION BY is used to divide the result set into partitions, while ORDER BY is used to sort the rows within each partition in window functions.

• PARTITION BY is used to group rows with the same values in specified columns

• ORDER BY is used to sort the rows within each partition

• Example: SELECT column1, column2, SUM(column3) OVER (PARTITION BY column1 ORDER BY column2) AS total FROM table_name

SQL is a programming language used for managing and analyzing data in relational databases.

• SQL stands for Structured Query Language

• It is used to retrieve, manipulate, and analyze data stored in relational databases

• SQL is important in data analytics as it allows analysts to query databases to extract relevant information for analysis

• It helps in filtering, sorting, and aggregating data to generate insights

• Examples of SQL commands include SELECT, INSERT, UPDATE, and DELETE

Different SQL joins yield varying row counts based on table relationships and join types.

• INNER JOIN: Returns rows with matching values in both tables. Example: If Table A has 5 rows and Table B has 3 matching rows, result = 3.

• LEFT JOIN: Returns all rows from the left table and matched rows from the right table. Example: If Table A has 5 rows and Table B has 2 matches, result = 5.

• RIGHT JOIN: Returns all rows from the right table and matched rows from the left table. Example: I...read more

WHERE clause is used to filter rows before grouping, while HAVING clause is used to filter groups after grouping.

• WHERE clause is used with SELECT, UPDATE, DELETE statements to filter rows based on a condition

• HAVING clause is used with SELECT statement to filter groups based on a condition

• WHERE clause is applied before the data is grouped, while HAVING clause is applied after the data is grouped

• Example: SELECT * FROM table_name WHERE column_name = 'value';

• Example: SELECT colum...read more

VLOOKUP is a powerful Excel function, but it has limitations and specific use cases in data analysis.

• 1. Limitations of VLOOKUP: It can only search for values in the first column of a range.

• 2. VLOOKUP is used for looking up and retrieving data from a specific column in a table based on a matching value.

• 3. Example of VLOOKUP: =VLOOKUP(A2, B2:D10, 2, FALSE) retrieves data from the second column where A2 matches the first column.

Data analysis involves several steps including data collection, data cleaning, data exploration, data modeling, and data visualization.

• Data collection: Gathering relevant data from various sources.

• Data cleaning: Removing any errors, inconsistencies, or missing values from the data.

• Data exploration: Analyzing the data to understand its characteristics and identify patterns or trends.

• Data modeling: Applying statistical or machine learning techniques to build models and make pre...read more

Indexing is a technique used to optimize data retrieval in databases by creating indexes on columns.

• Types of indexing include clustered and non-clustered indexes

• Clustered indexes physically reorder the data in the table based on the index key

• Non-clustered indexes create a separate structure to store the index key and a pointer to the actual data

• Indexes are used to speed up data retrieval operations such as SELECT queries

DDL is used to define the structure of database objects, while DML is used to manipulate data within those objects.

• DDL is used to create, modify, and delete database objects such as tables, indexes, and views.

• DML is used to insert, update, retrieve, and delete data within those database objects.

• DDL statements include CREATE, ALTER, DROP, TRUNCATE, etc.

• DML statements include SELECT, INSERT, UPDATE, DELETE, etc.

• DDL changes the structure of the database, while DML changes the co...read more

Handled cases include data cleaning, analysis, visualization and reporting for various industries.

• Data cleaning and analysis for a retail company to identify sales trends

• Visualization of customer behavior for a telecommunications company

• Reporting on website traffic for an e-commerce business

• Data analysis for a healthcare provider to improve patient outcomes

• Cleaning and analyzing survey data for a non-profit organization

Malaria is a mosquito-borne infectious disease caused by parasites. Drug allergy is an adverse reaction to medication. Hypertension is high blood pressure. Diabetes is a metabolic disorder affecting blood sugar levels. Obesity is excessive body weight. GERD is gastroesophageal reflux disease. Gout is a form of arthritis. Hyperlipidemia is high levels of lipids in the blood. Agar agar is a gelatinous substance derived from seaweed. Pigment names refer to various coloring agent...read more

TRUNCATE removes all rows from a table, DELETE removes specific rows, and DROP deletes the entire table structure.

• TRUNCATE is faster than DELETE as it does not log individual row deletions.

• DELETE is slower than TRUNCATE as it logs each row deletion.

• DROP removes the entire table structure along with all data.

• TRUNCATE and DELETE can be rolled back, but DROP cannot be rolled back.

• Example: TRUNCATE table_name;

• Example: DELETE FROM table_name WHERE condition;

• Example: DROP TABLE tab...read more

Window functions like ROW_NUMBER(), RANK(), and DENSE_RANK() assign a unique number to each row based on specified criteria.

• ROW_NUMBER() assigns a unique sequential integer starting from 1 to each row within a partition

• RANK() assigns a unique rank to each row within a partition, with no gaps in ranking if there are ties

• DENSE_RANK() assigns a unique rank to each row within a partition, with possible gaps in ranking if there are ties

A foreign key in relational databases is a field that links two tables together, establishing a relationship between them.

• A foreign key in one table points to the primary key in another table

• It ensures referential integrity by enforcing relationships between tables

• Foreign keys help maintain data consistency and prevent orphaned records

• Example: In a database with tables for 'orders' and 'customers', the 'customer_id' in the 'orders' table would be a foreign key linking to the ...read more

To build a dashboard, identify metrics, gather data, choose visualization tools, and ensure user-friendly design.

• Identify key business metrics: e.g., sales growth, customer acquisition cost, and churn rate.

• Gather data from relevant sources: e.g., CRM systems, Google Analytics, and financial databases.

• Choose visualization tools: e.g., Tableau, Power BI, or Google Data Studio for effective data representation.

• Design user-friendly layout: prioritize important metrics, use clear ...read more

I handle missing or corrupted data by identifying, analyzing, and applying appropriate techniques to ensure data integrity.

• Identify missing data using methods like 'isnull()' in Python's pandas library.

• Analyze the extent of missing data to determine if it's significant enough to impact results.

• Use imputation techniques, such as replacing missing values with the mean or median, to maintain dataset size.

• Consider removing rows or columns with excessive missing data if they don't...read more

Null values in an Excel sheet can be found by using filters or functions like ISBLANK or COUNTBLANK.

• Use filters to easily identify blank cells in the Excel sheet

• Use functions like ISBLANK or COUNTBLANK to check for null values in specific cells

• Look for cells with no data or missing values, which indicate null values

I have a solid understanding of SQL, including writing queries and using nested queries for data analysis.

• Proficient in SELECT statements to retrieve data from tables. Example: SELECT * FROM patients WHERE age > 30;

• Experienced in using JOINs to combine data from multiple tables. Example: SELECT a.name, b.disease FROM patients a JOIN diagnoses b ON a.id = b.patient_id;

• Skilled in using aggregate functions like COUNT, AVG, and SUM. Example: SELECT COUNT(*) FROM appointments WHER...read more

OpenAI Whisper is a speech recognition model designed for transcribing and translating audio into text.

• Whisper is an automatic speech recognition (ASR) system that can transcribe spoken language into written text.

• It supports multiple languages, making it versatile for global applications.

• Applications include transcription services for podcasts, meetings, and interviews.

• It can also be used for real-time translation in multilingual settings.

• Whisper is beneficial in accessibilit...read more

PowerBI and Tableau are both popular data visualization tools, but they have some key differences in terms of features and functionality.

• PowerBI is a Microsoft product, while Tableau is developed by Tableau Software.

• PowerBI is more user-friendly and integrates well with other Microsoft products, while Tableau offers more advanced visualization capabilities.

• Tableau has a feature called Calculated Field which allows users to create new fields based on existing data, while Power...read more

C is a procedural programming language while C++ is an object-oriented programming language.

• C++ is an extension of C with added features like classes, inheritance, and polymorphism.

• C++ is used for developing software applications, games, and operating systems.

• Website testing is the process of checking the functionality, usability, and performance of a website.

• It involves testing the website's links, forms, navigation, and compatibility with different devices and browsers.

• Webs...read more

VLOOKUP can be used to find specific information in a table by matching a key value.

• Use VLOOKUP to find a student's grade based on their student ID in a table of student data

• VLOOKUP can be used to retrieve a customer's contact information based on their customer ID

• It can also be used to look up product prices based on product codes in a pricing table

Merge two sorted linked lists by creating a linked list class and method to generate linked lists from scratch.

• Create a Node class with data and next pointer

• Create a LinkedList class with methods to insert nodes and merge two lists

• Iterate through both lists and compare nodes to merge them in sorted order

Pandas is a powerful Python library for data manipulation and analysis, offering flexible data structures and tools for handling complex datasets.

• Data Structures: Provides DataFrame and Series for easy data manipulation.

• Data Cleaning: Simplifies handling missing data with functions like dropna() and fillna().

• Data Analysis: Offers built-in functions for statistical analysis, e.g., mean(), median().

• Data Visualization: Integrates well with libraries like Matplotlib for visualizi...read more

Identifying data types in an Excel sheet involves recognizing categorical, numerical, date, and text data formats.

• Categorical data: Represents categories (e.g., 'Male', 'Female').

• Numerical data: Represents numbers (e.g., '25', '100.5').

• Date data: Represents dates (e.g., '2023-10-01').

• Text data: Represents strings (e.g., 'Patient Name').

Handling null values involves identifying, analyzing, and deciding on the best method to manage missing data in datasets.

• Identify null values using functions like isnull() in pandas.

• Analyze the impact of null values on your analysis; for example, if a column has 90% nulls, it may be better to drop it.

• Impute missing values using mean, median, or mode for numerical data; for example, replacing null ages with the average age.

• Use forward fill or backward fill methods for time ser...read more

I am familiar with basic SQL commands such as SELECT, INSERT, UPDATE, DELETE, JOIN, and GROUP BY.

• SELECT: Retrieve data from a database table

• INSERT: Add new records to a table

• UPDATE: Modify existing records in a table

• DELETE: Remove records from a table

• JOIN: Combine rows from two or more tables based on a related column

• GROUP BY: Group rows that have the same values into summary rows