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Data analyst interview questions

Data analyst interview questions for freshers test SQL (joins, GROUP BY, window functions), Excel (lookups and pivot tables), basic statistics (mean, median, standard deviation, outliers), data cleaning and how you explain findings. Most rounds add a case question, such as why sales dropped last week, and a walk-through of a dashboard or project you built.

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  • 30 questions with answers

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SQL examples use two tables: employees (id, name, dept_id, salary, joined_on) and departments (id, name).

Questions with answers30in 5 groups
SQL
10

Basic data analyst interview questions for freshers

5 questions

  1. What does a data analyst do?

    Basic

    A data analyst collects data, cleans it, analyses it to answer business questions and presents the answers in reports and dashboards that help teams decide, such as which products to stock or why customers leave.

  2. What are the steps of a data analysis project?

    Basic

    Define the question, collect the data, clean it, explore and analyse it, visualise the results, and share the findings with a recommendation. Then check whether the decision worked.

  3. What is the difference between data analysis and data science?

    Basic

    Data analysis mostly explains what happened and why, using SQL, Excel and dashboards. Data science more often predicts what will happen, using statistics, programming and machine-learning models. The roles overlap, and many analysts grow into data science.

  4. What is the difference between structured and unstructured data?

    Basic

    Structured data fits rows and columns with fixed fields, such as a sales table. Unstructured data has no fixed format, such as emails, images, call recordings and social media posts.

  5. What tools does a data analyst use?

    Basic

    SQL to pull and join data, Excel or Google Sheets for quick analysis, a BI tool such as Power BI or Tableau for dashboards, and often Python (pandas) or R for larger or repeated work.

SQL interview questions for data analysts

10 questions

  1. What are the types of joins?

    Basic

    INNER JOIN returns only matching rows from both tables. LEFT JOIN returns every row from the left table, with NULLs where the right table has no match. RIGHT JOIN does the reverse. FULL OUTER JOIN returns all rows from both. A CROSS JOIN returns every combination of rows.

    SELECT e.name, d.name AS department
FROM employees e
LEFT JOIN departments d ON e.dept_id = d.id;

  2. What is the difference between WHERE and HAVING?

    Basic

    WHERE filters rows before grouping and cannot use aggregates. HAVING filters groups after GROUP BY and can use aggregates such as COUNT or AVG.

    SELECT dept_id, AVG(salary) AS avg_salary
FROM employees
WHERE joined_on >= '2024-01-01'
GROUP BY dept_id
HAVING AVG(salary) > 600000;

  3. In what order does SQL run the clauses of a query?

    Intermediate

    FROM and JOIN, then WHERE, GROUP BY, HAVING, SELECT, DISTINCT, ORDER BY and finally LIMIT. That is why a column alias from SELECT cannot be used in WHERE.

  4. How do you find the second highest salary?

    Intermediate

    One way is to take the highest salary that is lower than the maximum. A window function such as DENSE_RANK also handles ties and works for the Nth highest.

    SELECT MAX(salary) FROM employees
WHERE salary < (SELECT MAX(salary) FROM employees);

SELECT DISTINCT salary FROM (
  SELECT salary, DENSE_RANK() OVER (ORDER BY salary DESC) AS rnk
  FROM employees
) t WHERE rnk = 2;

  5. How do you find duplicate rows?

    Basic

    Group by the columns that should be unique and keep the groups with more than one row.

    SELECT name, COUNT(*) AS copies
FROM employees
GROUP BY name
HAVING COUNT(*) > 1;

  6. What is the difference between RANK, DENSE_RANK and ROW_NUMBER?

    Intermediate

    All three number rows in an order. ROW_NUMBER gives every row a unique number, even with ties. RANK gives tied rows the same number and then skips (1, 1, 3). DENSE_RANK gives ties the same number without gaps (1, 1, 2).

  7. What is the difference between UNION and UNION ALL?

    Basic

    Both stack the results of two queries with the same columns. UNION removes duplicate rows; UNION ALL keeps them and is faster.

  8. How does NULL behave in SQL?

    Intermediate

    NULL means unknown, so NULL = NULL is not true. Use IS NULL or IS NOT NULL to test it, and COALESCE to replace it with a default. COUNT(column) skips NULLs; COUNT(*) counts every row.

  9. What are primary and foreign keys?

    Basic

    A primary key uniquely identifies each row in a table and cannot be NULL. A foreign key is a column that refers to the primary key of another table, such as employees.dept_id pointing to departments.id, which keeps the data consistent.

  10. How do you calculate a running total?

    Advanced

    With SUM as a window function, ordered by date. ROWS makes the total grow one row at a time even when two rows share a date.

    SELECT joined_on, salary,
       SUM(salary) OVER (ORDER BY joined_on, id ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS running_total
FROM employees;

Statistics questions for data analysts

6 questions

  1. When do you use the median instead of the mean?

    Basic

    When the data is skewed or has outliers. Salaries are the classic example: a few very high salaries pull the mean up, while the median shows what a typical person earns.

  2. What does standard deviation tell you?

    Basic

    How spread out the values are around the mean. A small standard deviation means most values are close to the average; a large one means they vary a lot.

  3. How do you find outliers?

    Intermediate

    Two common ways: values more than 1.5 times the interquartile range (IQR) below the first quartile or above the third quartile, or values more than about three standard deviations from the mean. Always check an outlier before removing it: it may be a data error or a real, important case.

  4. What is the difference between correlation and causation?

    Basic

    Correlation means two things move together; causation means one causes the other. Ice-cream sales and drowning both rise in summer, but one does not cause the other: hot weather drives both. Proving causation needs an experiment, such as an A/B test.

  5. What is an A/B test?

    Intermediate

    An experiment that randomly splits users into two groups, shows each a different version (such as two checkout pages) and compares a metric such as conversion rate, to see whether the difference is real or chance.

  6. What is a p-value, in simple words?

    Advanced

    The probability of seeing a result at least as extreme as yours if there were really no effect. A small p-value, commonly below 0.05, suggests the result is unlikely to be chance alone. It does not tell you how big or important the effect is.

Data cleaning, Excel and visualisation questions

6 questions

  1. How do you handle missing values?

    Basic

    First find out why they are missing. Then remove the rows if they are few and random, fill them with a sensible value (median, mode, previous value or a "Not given" category), or keep them flagged. Note what you did, because it changes the results.

  2. What does data cleaning involve?

    Basic

    Removing duplicates, fixing data types (dates stored as text), standardising entries ("Bengaluru" and "Bangalore"), trimming spaces, handling missing values and outliers, and checking that totals match the source.

  3. Which Excel skills does a data analyst need?

    Basic

    Lookups (VLOOKUP, INDEX-MATCH or XLOOKUP), SUMIFS and COUNTIFS, IF and IFERROR, pivot tables, conditional formatting, text and date functions and charts. See our Excel interview questions for answers.

  4. How do you choose the right chart?

    Basic

    Line charts for trends over time, bar charts to compare categories, a scatter plot for the relationship between two numbers, a histogram for a distribution, and a single big number (a card) for one key metric. Avoid pie charts with more than a few slices.

  5. What makes a good dashboard?

    Intermediate

    It answers a clear question for a named audience, puts the most important numbers at the top, uses few colours and charts, shows comparisons (target, last month), and lets users filter without breaking it.

  6. What is a KPI? Give an example.

    Basic

    A key performance indicator is a number that shows whether a goal is being met. For an online store: conversion rate, average order value, repeat purchase rate and return rate.

Case and scenario questions for data analysts

Interviewers care about your structure more than the final answer. Ask clarifying questions, then break the problem down.

3 questions

  1. Sales dropped 15% last week. How would you investigate?

    Intermediate

    Check the data first (a tracking or loading error?). Then compare with the same week last year for seasonality, and break the drop down by region, product, channel and customer type to find where it is concentrated. Look for causes in that segment: price changes, stock-outs, a competitor offer, a site issue. Report the finding with a recommendation.

  2. How would you explain a technical finding to a non-technical manager?

    Basic

    Lead with the answer and what to do, in one sentence. Then show one simple chart that supports it, give the size of the effect in business terms (rupees, customers, days), and keep the method for questions.

  3. Tell us about a project you are proud of.

    Basic

    Use one project and the same order every time: the question, the data and its size, what you cleaned, the analysis, the result (with a number if you have one) and what you would do differently. Keep it under two minutes.

How to prepare for a data analyst interview

  1. Practise SQL every day on sample tables: joins, GROUP BY with HAVING, subqueries, CASE WHEN and the window functions ROW_NUMBER, RANK, DENSE_RANK and SUM OVER.

  2. Build two portfolio projects on public Indian data, such as sales, census or cricket data: one SQL analysis and one dashboard in Power BI or Tableau. Write a short summary of each.

  3. Revise the statistics basics: mean, median, mode, standard deviation, percentiles, outliers, correlation and what an A/B test is.

  4. Practise three case questions aloud with a friend: a sudden drop in a metric, choosing between two options, and sizing something.

  5. Prepare your Excel and Power BI answers too; our Power BI interview questions cover DAX and modelling.

What is the interview process for a data analyst fresher?

It varies by company, but a common pattern is an online test (aptitude, SQL and sometimes Excel), a technical interview on SQL, statistics and your projects, sometimes a take-home task or a case question, and then an HR round. Customer-facing analyst roles in BPO and operations teams often test Excel more than SQL; see our BPO interview questions for those rounds.

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Questions freshers ask

Yes. B.Com, B.Sc, BBA and BA graduates become data analysts. What matters is SQL, Excel, one BI tool, basic statistics and projects that show you can turn data into a clear answer.

Not always. Many fresher roles ask only for SQL, Excel and Power BI or Tableau. Python with pandas helps you stand out and becomes important as you move to larger data or data science.

Joins, WHERE versus HAVING, GROUP BY, the second highest salary, finding duplicates, RANK versus DENSE_RANK versus ROW_NUMBER, UNION versus UNION ALL, NULL handling and running totals with window functions.