Lesson · Hinglish · ⏱ 7 min padhne mein

🗄️ SQL basics: database se sawaal poochna

Q: Kaunsa clause sirf ₹500 se upar ke orders rakhega?

WHERE amount > 500. WHERE condition se rows filter karta hai. ORDER BY sirf sort karta hai.

🏠 Asli zindagi ki misaal

Library mein ek catalogue hota hai. Aap har shelf nahi dhoondhte. Aap poochte ho: 'Premchand ki saari books dikhao jo 1920 ke baad chhapi, title ke hisaab se sorted.' SQL database se bilkul aisa sawaal poochne ki language hai.

💡 Aasaan shabdon mein

Zyaadatar company data relational databases mein hota hai: rows aur columns wali tables. SQL (Structured Query Language) us data ko padhta hai. SELECT columns chunta hai, FROM table chunta hai, WHERE rows filter karta hai, ORDER BY sort karta hai, aur LIMIT rows ki ginti limit karta hai. COUNT, SUM aur AVG jaise aggregates data ka summary nikaalte hain. GROUP BY har group ka ek summary deta hai, aur HAVING un groups ko filter karta hai. Lagbhag har data, ML aur AI-product role mein SQL har hafte use hota hai.

🪜 Step by step

Jo columns chahiye unhe table se SELECT karo: SELECT name, city FROM customers;
WHERE se rows filter karo: WHERE city = 'Pune' AND signup_date >= '2026-01-01'.
GROUP BY se summarise karo: SELECT city, COUNT(*) AS customers FROM customers GROUP BY city;
Groups ko HAVING se filter karo (grouping ke baad) aur ORDER BY ... DESC se sort karo, phir top 10 ke liye LIMIT 10.
Free sample database (SQLite, ya online SQL playgrounds) pe asli business sawaalon ke saath practice karo.

🔑 Zaroori shabd

SELECT … FROM: Kaunse columns padhne hain, aur kis table se.
WHERE: Sirf woh rows rakho jo condition match karti hain.
GROUP BY: Har group ka summary, jaise har city ke orders.

👀 Example dekho

sql

SELECT city, COUNT(*) AS orders, AVG(amount) AS avg_bill
FROM orders
WHERE order_date >= '2026-01-01'
GROUP BY city
HAVING COUNT(*) > 100
ORDER BY orders DESC
LIMIT 5;

Is saal ki top 5 sabse busy cities, aur unka average bill.

⚠️ Aam galtiyaan jinse bachna hai

Aggregates ko WHERE se filter karna: WHERE COUNT(*) > 5 fail hoga. Groups ki conditions ke liye HAVING use karo.
NULL ko = se compare karna. IS NULL ya IS NOT NULL use karo.
Production ki badi tables pe SELECT *. Sirf zaroori columns select karo; tez aur sasta hai.

✅ Jaldi se check karo

Kaunsa clause sirf ₹500 se upar ke orders rakhega?

WHERE amount > 500
ORDER BY amount
GROUP BY amount

Jawaab dekho

A. WHERE amount > 500: WHERE condition se rows filter karta hai. ORDER BY sirf sort karta hai.

🙋 Seekhne wale yeh poochhte hain

Kaunsa SQL seekhun: MySQL, PostgreSQL, SQL Server?

Basics sab mein lagbhag same hain. PostgreSQL accha default hai; baad mein aasaani se switch kar sakte ho.

AI roles ko SQL kyun chahiye?

Zyaadatar company data databases aur warehouses mein hota hai. Training data, evaluation data aur metrics aksar SQL query se shuru hote hain.

📌 Yaad rakho

SELECT kya → FROM kahan se → WHERE kaunsi rows → GROUP BY → ORDER BY.

Poora course, aapke roadmap ke hisaab se

Progress tracking, quick checks aur step-by-step order ke saath. Yeh lesson in courses ka hissa hai:

AI Foundations Path · Data Engineer (AI focus) · AI Product Manager

Course mein seekho