Q: What are window functions? Give a use case.

They compute across related rows without collapsing them - running totals, ranking within a group, comparing with the previous month using LAG().

Q: How do you handle missing data?

First find out why it's missing. Then remove rows if few and random, fill with a sensible value (median, previous value) if justified, or flag it. Always say what you did in your analysis.

Q: Mean or median - which would you report for salaries?

Median, because a few very high salaries pull the mean up. Use the mean when the data is roughly symmetric.

Q: How would you build a pivot table to show sales by region and month?

Region in rows, month in columns, sum of sales in values; add a filter for product. Mention XLOOKUP or VLOOKUP to bring in data from another sheet first.

Q: Sales dropped 15% last month. How would you investigate?

Confirm the data is right, then break the drop down: by region, product, channel, new vs returning customers. Check external causes (season, pricing changes, outages) and present the biggest driver with evidence. Example: "I'd first check the tracking didn't break. Then I'd split the drop by channel and region; if one channel explains most of it, I'd look at what changed there - a campaign ending, a price change or a site issue - and bring the top two causes with numbers to the team."

Q: Which charts would you use to show a trend, a comparison and a share?

Line chart for trends over time, bar chart for comparing categories, and a stacked bar or (sparingly) a pie for shares. Avoid 3D charts and cluttered dashboards.

Q: Tell me about an analysis that changed a decision.

Describe the question, the data and method, the finding and what the business did. Freshers can use a college or Kaggle project and explain the conclusion clearly.

Question 1

What is the difference between INNER JOIN and LEFT JOIN?

Accepted Answer

INNER JOIN keeps only rows that match in both tables; LEFT JOIN keeps every row from the left table, with NULLs where there's no match. Give an example: all customers, including those with no orders.

Question 2

WHERE vs HAVING?

Accepted Answer

WHERE filters rows before grouping; HAVING filters groups after aggregation - for example HAVING COUNT(*) > 5.

Question 3

Write a query for the second-highest salary.

Accepted Answer

Use DENSE_RANK() OVER (ORDER BY salary DESC) and pick rank 2, or SELECT MAX(salary) WHERE salary < (SELECT MAX(salary)). Mention how each handles ties.

Question 4

What are window functions? Give a use case.

Accepted Answer

They compute across related rows without collapsing them - running totals, ranking within a group, comparing with the previous month using LAG().

Question 5

How do you handle missing data?

Accepted Answer

First find out why it's missing. Then remove rows if few and random, fill with a sensible value (median, previous value) if justified, or flag it. Always say what you did in your analysis.

Question 6

Mean or median - which would you report for salaries?

Accepted Answer

Median, because a few very high salaries pull the mean up. Use the mean when the data is roughly symmetric.

Question 7

How would you build a pivot table to show sales by region and month?

Accepted Answer

Region in rows, month in columns, sum of sales in values; add a filter for product. Mention XLOOKUP or VLOOKUP to bring in data from another sheet first.

Question 8

Sales dropped 15% last month. How would you investigate?

Accepted Answer

Confirm the data is right, then break the drop down: by region, product, channel, new vs returning customers. Check external causes (season, pricing changes, outages) and present the biggest driver with evidence. Example: "I'd first check the tracking didn't break. Then I'd split the drop by channel and region; if one channel explains most of it, I'd look at what changed there - a campaign ending, a price change or a site issue - and bring the top two causes with numbers to the team."

Question 9

Which charts would you use to show a trend, a comparison and a share?

Accepted Answer

Line chart for trends over time, bar chart for comparing categories, and a stacked bar or (sparingly) a pie for shares. Avoid 3D charts and cluttered dashboards.

Question 10

Tell me about an analysis that changed a decision.

Accepted Answer

Describe the question, the data and method, the finding and what the business did. Freshers can use a college or Kaggle project and explain the conclusion clearly.

Question 11

What skills are needed for a data analyst job?

Accepted Answer

Strong SQL, Excel, one BI tool such as Power BI or Tableau, basic statistics and the ability to explain findings simply. Python is a plus for many roles.

Question 12

Can a fresher get a data analyst job?

Accepted Answer

Yes. Build two or three projects with real datasets, publish dashboards, and practise SQL interview questions until joins and window functions feel easy.

Question 13

Is Python required for data analyst interviews?

Accepted Answer

Not always. SQL and Excel are essential; Python with pandas is asked at many product and analytics companies.

Data analyst interview questions and answers

What to revise before the interview

1.What is the difference between INNER JOIN and LEFT JOIN?

2.WHERE vs HAVING?

3.Write a query for the second-highest salary.

4.What are window functions? Give a use case.

5.How do you handle missing data?

6.Mean or median - which would you report for salaries?

7.How would you build a pivot table to show sales by region and month?

8.Sales dropped 15% last month. How would you investigate?

9.Which charts would you use to show a trend, a comparison and a share?

10.Tell me about an analysis that changed a decision.

Frequently asked questions

Company interview guides for this role

Related roles and topics

Practise these questions for your next interview