#Sql Subquery

This SQL query looks completely reasonable. It filters out banned and inactive users. Yet the result might catch you off guard. What does it actually return?

Day 15/21 – SQL Challenge (Revision Day) Today was all about revising key SQL patterns and reinforcing concepts through mixed problems. • LC 550 – Game Analysis IV: Used date comparison logic to calculate player retention based on consecutive login days. • SS 10350 – Users by Avg Session Time: Calculated average session duration per user using aggregation and time difference logic. • SS 10142 – Customers with No Orders: Solved using LEFT JOIN and null filtering to identify customers without any orders. • SS 2097 – Premium Account: Used conditional aggregation to compare premium vs non-premium user behavior. • LC 1484 – Group Products Sold by Date: Grouped products by sell date and used aggregation to list products sold each day. • DL – Tweets Rolling Average: Applied window functions to calculate rolling averages over time. • LC 626 – Exchange Seats (Revision): Revisited odd/even swap logic and handled edge cases cleanly. • LC 1789 – Primary Department for Each Employee (Revision): Handled single vs multiple department scenarios using count and primary flag logic. Key learning: Revision helps connect patterns—most SQL problems reuse the same core ideas.

Can You Solve This SQL Recursion Problem? 😈🔥 Recursive queries in SQL confuse most developers 🤯 But once you understand them, advanced queries become easy 😎 In this video, I explain SQL recursion using Recursive CTE step by step. You’ll learn: ✔️ What is Recursive CTE ✔️ How base case works ✔️ How recursion builds rows ✔️ How to stop infinite loops ✔️ Real interview use cases If you’re preparing for SQL interviews, this is a must-watch 🚀 Save this video 📌 Follow @Door2Dev for daily SQL tips 💙 #sql #postgresql #cte #recursion #codinginterview

🧠 SQL Subquery MCQs That Kill Confusion 😈 4️⃣9️⃣ Which operator returns TRUE only if all values match? ✅ ALL 👉 Condition must satisfy every value returned 🔥 5️⃣0️⃣ A correlated subquery executes? ✅ For each row of outer query 👉 Runs again & again per row 😳 (performance impact!) 5️⃣1️⃣ Which subquery depends on outer query? ✅ Correlated subquery 👉 Inner query references outer query columns 🔗 😵 Subqueries look simple… logic isn’t. 💬 Comment your score: 0/3 | 1/3 | 2/3 | 3/3 👥 Tag a friend scared of correlated subqueries 😅 ❤️ Save this for SQL interview prep ➡️ Follow for daily SQL MCQs & placement content #SQLMCQs #SQLReels #Subquery #SQLInterview #DatabaseConcepts CodingReels PlacementPreparation DeveloperLife 🚀

🚀 𝐃𝐀𝐘 𝟏𝟓 – 𝐒𝐐𝐋 𝐈𝐧𝐭𝐞𝐫𝐯𝐢𝐞𝐰 𝐐𝐮𝐞𝐬𝐭𝐢𝐨𝐧 𝐒𝐞𝐫𝐢𝐞𝐬 Simple question… but many get confused 👀 👉 𝐖𝐡𝐢𝐜𝐡 𝐒𝐐𝐋 𝐜𝐥𝐚𝐮𝐬𝐞 𝐢𝐬 𝐮𝐬𝐞𝐝 𝐭𝐨 𝐜𝐨𝐦𝐛𝐢𝐧𝐞 𝐫𝐨𝐰𝐬 𝐟𝐫𝐨𝐦 𝐭𝐰𝐨 𝐭𝐚𝐛𝐥𝐞𝐬? A. MERGE B. JOIN C. CONNECT D. UNION ALL No Google. No hints. Think like a real developer 👨‍💻 👇 Comment your answer: A / B / C / D 📌 Follow @𝐒𝐡𝐨𝐫𝐭𝐭𝐫𝐢𝐜𝐤 for daily SQL interview challenges 📌 Save this for revision before your interview #SQLInterview #SQLChallenge #LearnSQL #SQLMCQ #SQLQueries #Database #DBMS #DataAnalyst #SQLDeveloper #BackendDeveloper #CodingLife #DeveloperLife #InterviewPrep

🧠 SQL MCQs That Separate Average from Advanced 😈 4️⃣3️⃣ EXISTS checks? ✅ Row existence 👉 Returns TRUE if subquery returns at least one row 🔥 4️⃣4️⃣ Faster for large data? ✅ EXISTS 👉 Stops scanning once match is found ⚡ 👉 Often better than IN for big datasets 😏 4️⃣5️⃣ Can subquery be used in SELECT? ✅ Yes 👉 Scalar subqueries inside SELECT are valid 👀 😳 Small keyword… massive performance difference 💬 Comment your score: 0/3 | 1/3 | 2/3 | 3/3 👥 Tag a friend who always uses IN 😅 ❤️ Save this for SQL interview prep ➡️ Follow for daily SQL MCQs & placement content #SQLMCQs #SQLReels #Subquery #SQLInterview #DatabaseConcepts CodingReels PlacementPreparation DeveloperLife 🚀

🧠 SQL MCQs That Interviewers Love to Ask 😈 5️⃣5️⃣ Does a View store data physically? ❌ No 👉 It’s a virtual table 👉 Data stays in original tables 🔥 5️⃣6️⃣ Which clause is mandatory in SELECT? ✅ FROM 👉 Without FROM… no table to fetch data from 😏 5️⃣7️⃣ Which MySQL function converts NULL to a value? ✅ IFNULL() 👉 Replaces NULL with a default value ⚡ 😳 Tiny concepts… huge interview impact 💬 Comment your score: 0/3 | 1/3 | 2/3 | 3/3 👥 Tag a friend who forgets IFNULL 😅 ❤️ Save this for SQL revision ➡️ Follow for daily SQL MCQs & placement prep #SQLMCQs #SQLReels #MySQL #SQLInterview #DatabaseConcepts CodingReels PlacementPreparation DeveloperLife 🚀

🧠 SQL MCQs That Every Fresher Must Know 😈 5️⃣2️⃣ Which keyword returns unique rows? ✅ DISTINCT 👉 Removes duplicate records instantly 🔥 5️⃣3️⃣ View is a? ✅ Virtual table 👉 Doesn’t store data physically 👉 Shows data from original tables 👀 5️⃣4️⃣ Which command creates a view? ✅ CREATE VIEW 👉 Saves complex queries for reuse ⚡ 😳 Small keywords… big database impact 💬 Comment your score: 0/3 | 1/3 | 2/3 | 3/3 👥 Tag a friend who forgets DISTINCT 😅 ❤️ Save this for SQL interview revision ➡️ Follow for daily SQL MCQs & placement prep #SQLMCQs #SQLReels #DatabaseConcepts #SQLInterview #LearnSQL CodingReels PlacementPreparation DeveloperLife 🚀

3 Consecutive Same Numbers — Not as Easy as It Looks! This is where SQL becomes real analytical thinking 🔥 At first glance, you might try: GROUP BY num HAVING COUNT(*) >= 3 ❌ But that won’t guarantee they are consecutive. The real trick? 👇 ✔ Use LAG() ✔ Use LEAD() ✔ Compare previous + next rows Because consecutive means sequence logic — not just count. This question tests: 🔹 Window functions 🔹 Sequential pattern detection 🔹 Interview-level problem solving Master this and streak-based problems become easy 🚀 #SQLInterview #WindowFunctions #AdvancedSQL #LearnSQL #DataEngineering

Day 21/21 – SQL Challenge (Final Day) Wrapped up the challenge with a mix of ranking, retention, distribution, and business logic problems. • SS 2007 – Rank Variance Per Country: Used window functions to rank records within each country and calculated the difference between rankings to measure variance. • DL – Histogram of Users and Purchases: Grouped users by purchase count and calculated frequency distribution to generate histogram-style output. • DL – Active User Retention: Compared user activity across consecutive days to calculate retention rate using date logic and aggregation. • DL – Well Paid Employees: Joined employee and department data and filtered employees earning more than department average. • LC SQL50 (2 Questions): Practiced core patterns like joins, filtering, and aggregation from the SQL50 set to strengthen fundamentals. • DL – SuperCloud Customer: Used grouping and conditional aggregation to identify customers meeting product usage criteria. Key learning from 21 Days: Most SQL problems repeat the same core ideas — joins, window functions, aggregation, filtering, and clear thinking. Consistency > complexity. 21 days done. On to bigger goals 🚀

Drop your answer in the comments below! If you're right, tag a friend who needs to level up their SQL game. Wrong? No worries – I'll reveal the answer later. Pro Tip: Mastering SQL can skyrocket your tech career. Follow for daily coding tips, quizzes, and hacks to become a database wizard! 💻🔥 #SQLQuiz #SQL #Database #Programming #TechTips CodingQuiz LearnSQL DeveloperLife DataScience TechCommunity InstaTech CodeWithMe SQLCommands TechHacks

Most people think these two are the same. They’re not. RANK() → Same rank for ties → Skips numbers DENSE_RANK() → Same rank for ties → No gaps Same data. Same order. Different outcomes. This is the kind of detail that separates someone who writes SQL from someone who understands SQL. Save this — you’ll need it. #SQL #DataAnalytics #WindowFunctions #TechLearning #BuildInPublic