10 SQL Queries Every Fresher Data Analyst Should Practise

Almost every data analyst interview in Bangalore has a SQL round. The good news: most questions come from a small set of patterns. If you can write these ten queries from memory and explain them, you are ready for most fresher interviews.

Imagine two tables: customers(id, name, city) and orders(id, customer_id, amount, order_date).

1. Filter and sort

Orders above 5,000, newest first: SELECT * FROM orders WHERE amount > 5000 ORDER BY order_date DESC;

2. Count per group

Customers per city: SELECT city, COUNT(*) FROM customers GROUP BY city;

3. Filter groups with HAVING

Cities with more than 100 customers: add HAVING COUNT(*) > 100. Interviewers often ask how HAVING differs from WHERE: WHERE filters rows before grouping, HAVING filters groups after.

4. INNER JOIN

Each order with the customer's name: SELECT o.id, c.name, o.amount FROM orders o JOIN customers c ON c.id = o.customer_id;

5. LEFT JOIN to find missing data

Customers who never ordered: SELECT c.name FROM customers c LEFT JOIN orders o ON o.customer_id = c.id WHERE o.id IS NULL;

6. Total and average per customer

SELECT customer_id, SUM(amount), AVG(amount) FROM orders GROUP BY customer_id;

7. Top N

Top 5 customers by spend: sort the query above by SUM(amount) DESC and add LIMIT 5.

8. Second highest value

A classic: SELECT MAX(amount) FROM orders WHERE amount < (SELECT MAX(amount) FROM orders);

9. Monthly totals

Group by month to show a trend: in MySQL, SELECT DATE_FORMAT(order_date, '%Y-%m') AS month, SUM(amount) FROM orders GROUP BY month;

10. Window functions

Rank customers inside each city: RANK() OVER (PARTITION BY city ORDER BY total DESC). Window functions come up more and more in interviews, so practise at least RANK, ROW_NUMBER and a running total.

How to practise

Create these two tables in MySQL with 20 to 30 rows of made-up data, then write each query without looking. Say out loud what it does. That habit of explaining your query clearly is what interviewers remember.

If you would like a guided path with Excel, SQL, Power BI, Tableau and Python, plus mock interviews, see the data analyst course in Bangalore at ScholarLogic, BTM Layout.

Arjun is a counselor at ScholarLogic. 

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