Data & AI
Data Analyst A comprehensive guide covering SQL, Python/R, Statistics, Data Visualization, Excel, Data Cleaning, Business Domain Knowledge, and Machine Learning basics for Data Analyst roles.
225 questions Updated 2026-02-03 Beginner Intermediate Advanced
What you will be asked about SQL & Database Python/R Statistics Visualization Excel Data Cleaning Business Knowledge General Concepts Machine Learning Tools Scenario Behavioral
How to prepare Go through the topic list above and mark every one you cannot explain for five minutes unprepared. Those are your gaps. Pair every concept with a story from your own work — interviewers probe depth, and depth comes from having actually done it. Do the DSA rounds anyway. Almost every role in this list still screens with coding. Prepare two projects you can whiteboard end to end, including what you would change now. Data Analyst interview questions225 1. What is the difference between WHERE and HAVING clauses? Beginner 2. Explain the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN. Beginner 3. What are window functions and when would you use them? Intermediate 4. How do you find duplicate records in a table? Beginner 5. What is the difference between DELETE, TRUNCATE, and DROP? Intermediate 6. Explain primary key vs foreign key. Beginner 7. What are indexes and why are they important? Intermediate 8. How do you optimize a slow-running SQL query? Advanced 9. What is a subquery and when would you use one? Intermediate 10. Explain GROUP BY and its use cases. Beginner 11. What is the difference between UNION and UNION ALL? Beginner 12. How do you handle NULL values in SQL? Beginner 13. What are CTEs (Common Table Expressions)? Intermediate 14. Explain the RANK, DENSE_RANK, and ROW_NUMBER functions. Intermediate 15. How do you find the second highest salary in a table? Intermediate 16. What is normalization and denormalization? Intermediate 17. Explain the different types of keys in SQL (candidate, composite, surrogate). Advanced 18. What is a self-join and when would you use it? Intermediate 19. How do you calculate running totals in SQL? Intermediate 20. What is the difference between correlated and non-correlated subqueries? Advanced 21. Explain CASE statements with examples. Beginner 22. What are aggregate functions? Name some common ones. Beginner 23. How do you use PARTITION BY in window functions? Intermediate 24. What is the difference between clustered and non-clustered indexes? Advanced 25. How do you find the Nth highest value in a table? Advanced 26. What are stored procedures and when would you use them? Intermediate 27. Explain the COALESCE function. Beginner 28. How do you perform date calculations in SQL? Intermediate 29. What is the difference between CHAR and VARCHAR? Beginner 30. How do you pivot and unpivot data in SQL? Advanced 31. What Python libraries do you use for data analysis? Beginner 32. Explain the difference between a list and a tuple. Beginner 33. What is pandas and why is it useful? Beginner 34. How do you handle missing data in pandas? Intermediate 35. What is the difference between loc and iloc? Intermediate 36. Explain list comprehension with an example. Beginner 37. What are lambda functions? Intermediate 38. How do you merge or join dataframes in pandas? Intermediate 39. What is NumPy and when would you use it? Beginner 40. How do you read CSV and Excel files in Python? Beginner 41. What is the difference between apply, map, and applymap in pandas? Advanced 42. How do you group data in pandas (groupby)? Intermediate 43. What are dictionaries in Python and when do you use them? Beginner 44. Explain broadcasting in NumPy. Advanced 45. How do you handle datetime data in pandas? Intermediate 46. What is the difference between shallow copy and deep copy? Advanced 47. How do you sort data in pandas? Beginner 48. What are generators in Python? Advanced 49. How do you filter data in pandas? Beginner 50. What is matplotlib and seaborn? Beginner 51. How do you create custom functions in Python? Beginner 52. What is the difference between Series and DataFrame? Beginner 53. How do you handle categorical data in pandas? Intermediate 54. What are pandas pivot tables? Intermediate 55. How do you optimize pandas code for large datasets? Advanced 56. What is the difference between mean, median, and mode? Beginner 57. Explain standard deviation and variance. Beginner 58. What is a p-value and how do you interpret it? Intermediate 59. What is the difference between correlation and causation? Beginner 60. Explain Type I and Type II errors. Intermediate 61. What is a confidence interval? Intermediate 62. What is the Central Limit Theorem? Advanced 63. Explain hypothesis testing. Intermediate 64. What is the difference between population and sample? Beginner 65. What are outliers and how do you detect them? Intermediate 66. Explain normal distribution. Beginner 67. What is statistical significance? Intermediate 68. What is the difference between parametric and non-parametric tests? Advanced 69. Explain regression analysis. Intermediate 70. What is the difference between descriptive and inferential statistics? Beginner 71. What is the difference between linear and logistic regression? Intermediate 72. Explain R-squared and adjusted R-squared. Advanced 73. What is the difference between one-tailed and two-tailed tests? Intermediate 74. What is probability distribution? Intermediate 75. Explain Bayes' Theorem. Advanced 76. What is sampling and what are different sampling methods? Intermediate 77. What is the law of large numbers? Intermediate 78. Explain skewness and kurtosis. Advanced 79. What is multicollinearity and how do you detect it? Advanced 80. What is the difference between covariance and correlation? Intermediate 81. What is a z-score? Beginner 82. Explain the t-test and when to use it. Intermediate 83. What is chi-square test? Advanced 84. What is ANOVA? Advanced 85. What is time series analysis? Advanced 86. What tools do you use for data visualization? Beginner 87. When would you use a bar chart vs a line chart? Beginner 88. What is Tableau and have you used it? Beginner 89. Explain the importance of data visualization. Beginner 90. What makes a good dashboard? Intermediate 91. How do you choose the right chart type? Intermediate 92. What is Power BI? Beginner 93. What are some best practices for data visualization? Intermediate 94. How do you visualize data in Python? Intermediate 95. What is the difference between a histogram and a bar chart? Beginner 96. When would you use a scatter plot? Beginner 97. What is a heat map and when would you use it? Intermediate 98. How do you handle too many categories in a visualization? Advanced 99. What is a box plot and what does it show? Intermediate 100. How do you make your visualizations accessible and easy to understand? Advanced 101. What Excel functions do you use most frequently? Beginner 102. Explain VLOOKUP and its limitations. Beginner 103. What is the difference between VLOOKUP and INDEX-MATCH? Intermediate 104. How do you create a pivot table? Beginner 105. What are some advanced Excel formulas you know? Advanced 106. How do you handle large datasets in Excel? Intermediate 107. What is Power Query? Intermediate 108. Explain conditional formatting. Beginner 109. How do you remove duplicates in Excel? Beginner 110. What is the difference between absolute and relative cell references? Beginner 111. What are array formulas in Excel? Advanced 112. How do you use SUMIF, SUMIFS, COUNTIF, COUNTIFS? Beginner 113. What is Power Pivot? Advanced 114. How do you create dynamic charts in Excel? Intermediate 115. What are Excel macros and VBA? Advanced 116. What is data cleaning and why is it important? Beginner 117. How do you handle missing values in a dataset? Intermediate 118. What is data normalization? Intermediate 119. How do you detect and handle outliers? Intermediate 120. What is ETL and have you worked with it? Intermediate 121. How do you deal with inconsistent data formats? Beginner 122. What is data validation? Beginner 123. How do you handle duplicate records? Beginner 124. What is data transformation? Intermediate 125. Explain the 80/20 rule in data cleaning. Beginner 126. What is feature engineering? Advanced 127. How do you handle imbalanced datasets? Advanced 128. What is data profiling? Intermediate 129. How do you validate your cleaned data? Intermediate 130. What is data standardization vs normalization? Advanced 131. How do you translate business requirements into analytical tasks? Intermediate 132. What KPIs have you worked with? Beginner 133. How do you communicate findings to non-technical stakeholders? Intermediate 134. What is A/B testing and when would you use it? Intermediate 135. How do you measure customer churn? Intermediate 136. What is customer segmentation? Beginner 137. How do you calculate ROI? Beginner 138. What business metrics are most important to track? Beginner 139. How do you prioritize analytical projects? Intermediate 140. Give an example of how your analysis impacted business decisions. Intermediate 141. What is funnel analysis? Intermediate 142. How do you measure customer lifetime value (CLV)? Intermediate 143. What is cohort analysis? Intermediate 144. How do you build a business case for your recommendations? Advanced 145. What is RFM analysis? Advanced 146. How do you measure marketing campaign effectiveness? Intermediate 147. What is the difference between leading and lagging indicators? Intermediate 148. How do you handle stakeholder disagreements about data interpretation? Advanced 149. What is revenue forecasting? Advanced 150. How do you measure product performance? Intermediate 151. What is the data analysis process you follow? Beginner 152. What is the difference between structured and unstructured data? Beginner 153. What is data warehousing? Intermediate 154. Explain OLAP vs OLTP. Intermediate 155. What is big data and have you worked with it? Intermediate 156. What is data modeling? Intermediate 157. What is the difference between quantitative and qualitative data? Beginner 158. What are data pipelines? Intermediate 159. What is data governance? Advanced 160. Explain dimensional modeling. Advanced 161. What is the star schema and snowflake schema? Advanced 162. What is data quality and how do you measure it? Intermediate 163. What is the difference between batch processing and real-time processing? Intermediate 164. What are fact and dimension tables? Intermediate 165. What is data lineage? Advanced 166. What is the difference between data lake and data warehouse? Intermediate 167. What is master data management? Advanced 168. What is metadata? Beginner 169. What are the challenges of working with big data? Intermediate 170. What is data migration? Intermediate 171. What is the difference between supervised and unsupervised learning? Intermediate 172. What is overfitting and underfitting? Intermediate 173. What is cross-validation? Advanced 174. Explain the bias-variance tradeoff. Advanced 175. What is feature selection and why is it important? Intermediate 176. What is clustering and name some clustering algorithms. Intermediate 177. What is classification vs regression? Beginner 178. What is a confusion matrix? Intermediate 179. What is precision vs recall? Intermediate 180. What is k-means clustering? Intermediate 181. What BI tools have you worked with? Beginner 182. Have you used Google Analytics? Explain key metrics. Intermediate 183. What is Git and version control? Beginner 184. What cloud platforms have you used (AWS, Azure, GCP)? Intermediate 185. What is Jupyter Notebook? Beginner 186. Have you worked with API integrations? Intermediate 187. What is Apache Spark? Advanced 188. What is Hadoop? Advanced 189. What database management systems have you used? Beginner 190. What is the difference between SQL and NoSQL databases? Intermediate 191. How would you analyze a sudden drop in user engagement? Advanced 192. A stakeholder questions your data findings. How do you respond? Intermediate 193. You're given a dataset with 80% missing values. What do you do? Advanced 194. How would you design a dashboard for executive leadership? Intermediate 195. Your SQL query is running too slowly. How do you troubleshoot? Advanced 196. Two data sources show conflicting numbers. How do you resolve this? Advanced 197. You need to present complex findings in 5 minutes. What's your approach? Intermediate 198. How would you analyze the success of a new product launch? Intermediate 199. You discover an error in a report you sent last week. What do you do? Intermediate 200. How would you identify factors driving customer churn? Advanced 201. You're asked to analyze data you don't have access to. How do you proceed? Beginner 202. How would you measure the impact of a price change? Advanced 203. Your analysis shows a result opposite to what the team expected. How do you handle it? Intermediate 204. How would you automate a repetitive reporting task? Intermediate 205. You have one week to learn a new tool for a project. How do you approach it? Beginner 206. How would you validate data from a third-party vendor? Intermediate 207. Your team disagrees on which metric to focus on. How do you decide? Intermediate 208. How would you analyze seasonal trends in sales data? Advanced 209. You're asked to reduce report generation time by 50%. What's your strategy? Advanced 210. How would you handle a request to manipulate data to show desired results? Advanced 211. Describe a challenging data project you worked on. Intermediate 212. How do you ensure data accuracy? Beginner 213. Tell me about a time you found an insight that changed business strategy. Intermediate 214. How do you handle tight deadlines? Beginner 215. What do you do when you don't know the answer to a data question? Beginner 216. How do you stay updated with data analysis trends? Beginner 217. Describe your experience working with cross-functional teams. Intermediate 218. How do you handle conflicting requirements from stakeholders? Intermediate 219. What's your approach to learning new tools or technologies? Beginner 220. Why do you want to be a Data Analyst? Beginner 221. Tell me about a time you made a mistake in your analysis. Intermediate 222. How do you manage multiple projects simultaneously? Beginner 223. Describe a time you had to explain technical concepts to a non-technical audience. Intermediate 224. What's the most complex dataset you've worked with? Advanced 225. How do you handle feedback and criticism on your work? Beginner