Whether you're applying for Data Analyst, BI, or Data Engineer roles — SQL rounds are must-clear. Here's your focused roadmap:
1️⃣ Core SQL Concepts
🔹 Understand RDBMS, tables, keys, schemas
🔹 Data types,
NULLs, constraints 🧠 Interview Tip: Be able to explain
Primary vs Foreign Key.2️⃣ Basic Queries
🔹
SELECT, FROM, WHERE, ORDER BY, LIMIT 🧠 Practice: Filter and sort data by multiple columns.
3️⃣ Joins – Very Frequently Asked!
🔹
INNER, LEFT, RIGHT, FULL OUTER JOIN 🧠 Interview Tip: Explain the difference with examples.
🧪 Practice: Write queries using joins across 2–3 tables.
4️⃣ Aggregations & GROUP BY
🔹
COUNT, SUM, AVG, MIN, MAX, HAVING 🧠 Common Question: Total sales per category where total > X.
5️⃣ Window Functions
🔹
ROW_NUMBER(), RANK(), DENSE_RANK(), LAG(), LEAD() 🧠 Interview Favorite: Top N per group, previous row comparison.
6️⃣ Subqueries & CTEs
🔹 Write queries inside
WHERE, FROM, and using WITH 🧠 Use Case: Filtering on aggregated data, simplifying logic.
7️⃣ CASE Statements
🔹 Add logic directly in
SELECT 🧠 Example: Categorize users based on spend or activity.
8️⃣ Data Cleaning & Transformation
🔹 Handle
NULLs, format dates, string manipulation (TRIM, SUBSTRING) 🧠 Real-world Task: Clean user input data.
9️⃣ Query Optimization Basics
🔹 Understand indexing, query plan, performance tips
🧠 Interview Tip: Difference between
WHERE and HAVING.🔟 Real-World Scenarios
🧠 Must Practice:
• Sales funnel
• Retention cohort
• Churn rate
• Revenue by channel
• Daily active users
🧪 Practice Platforms
• LeetCode (Easy–Hard SQL)
• StrataScratch (Real business cases)
• Mode Analytics (SQL + Visualization)
• HackerRank SQL (MCQs + Coding)
💼 Final Tip:
Explain why your query works, not just what it does. Speak your logic clearly.
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