✅ Useful SQL Concepts You Should Know 🚀📈

1️⃣ Constraints in SQL:

- PRIMARY KEY – Uniquely identifies each row
- FOREIGN KEY – Links to another table
- UNIQUE – Ensures all values are different
- NOT NULL – Column must have a value
- CHECK – Validates data before insert/update

2️⃣ SQL Views:

Virtual tables based on result of a query

CREATE VIEW top_students AS
SELECT name, marks FROM students WHERE marks > 90;

3️⃣ Indexing:

Improves query performance

CREATE INDEX idx_name ON employees(name);

4️⃣ SQL Transactions:

Ensure data integrity

BEGIN;
UPDATE accounts SET balance = balance - 100 WHERE id = 1;
UPDATE accounts SET balance = balance + 100 WHERE id = 2;
COMMIT;

5️⃣ Triggers:

Automatic actions when events occur

CREATE TRIGGER log_update
AFTER UPDATE ON employees
FOR EACH ROW
INSERT INTO logs(action) VALUES ('Employee updated');

6️⃣ Stored Procedures:

Reusable blocks of SQL logic

CREATE PROCEDURE getTopStudents()
BEGIN
  SELECT * FROM students WHERE marks > 90;
END;

7️⃣ Common Table Expressions (CTEs):

Temporary named result sets

WITH dept_count AS (
  SELECT department, COUNT(*) AS total FROM employees GROUP BY department
)
SELECT * FROM dept_count;

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