Post #2303

✅Top 10 SQL Interview Questions🔥 1️⃣What is a table and a field in SQL? ⦁ Table: Organized data in rows and columns ⦁ Field: A column representing data attribute 2️⃣Describe the SELECT statement. ⦁ Fetch data from one or more tables ⦁ Use WHERE to filter, ORDER BY to sort 3️⃣Explain SQL constraints. ⦁ Rules for data integrity: PRIMARY KEY, FOREIGN KEY, UNIQUE, NOT NULL, CHECK 4️⃣What is normalization? ⦁ Process to reduce data redundancy & improve integrity (1NF, 2NF, 3NF…) 5️⃣Explain different JOIN types with examples. ⦁ INNER, LEFT, RIGHT, FULL JOIN: Various ways to combine tables based on matching rows 6️⃣What is a subquery? Give example. ⦁ Query inside another query: SELECT name FROM employees WHERE department_id = (SELECT id FROM departments WHERE name='Sales'); 7️⃣How to optimize slow queries? ⦁ Use indexes, avoid SELECT *, simplify joins, reduce nested queries 8️⃣What are aggregate functions? Examples? ⦁ Perform calculations on sets: SUM(), COUNT(), AVG(), MIN(), MAX() 9️⃣What is SQL injection? How to prevent it? ⦁ Security risk manipulating queries ⦁ Prevent: parameterized queries, input validation 🔟How to find the Nth highest salary without TOP/LIMIT? SELECT DISTINCT salary FROM employees e1 WHERE N-1 = (SELECT COUNT(DISTINCT salary) FROM employees e2 WHERE e2.salary > e1.salary); 🔥Double Tap ❤️ For More!