✅ SQL for Data Science 🗄️📊

👉 SQL is one of the most important skills for Data Scientists and Data Analysts.

Almost every company stores data inside databases, and SQL helps retrieve and analyze that data.

🔹 1. What is SQL?
SQL = Structured Query Language

👉 Used to:
✔ Store data
✔ Retrieve data
✔ Filter data
✔ Analyze data

🔥 2. Common Database Systems
✔ MySQL
✔ PostgreSQL
✔ SQLite
✔ Microsoft SQL Server

🔹 3. Basic SQL Query

✅ SELECT Statement
Used to retrieve data from a table.

SELECT * FROM employees;

👉 ** means all columns.

🔹 4. Select Specific Columns
SELECT name, salary FROM employees;

🔹 5. WHERE Clause ⭐
Used for filtering data.

SELECT * FROM employees
WHERE salary > 50000;

🔹 6. ORDER BY
Sort data.

SELECT * FROM employees
ORDER BY salary DESC;

✔ ASC → Ascending
✔ DESC → Descending

🔹 7. Aggregate Functions ⭐
Used for calculations.

Function: COUNT()
Purpose: Count rows

Function: SUM()
Purpose: Total

Function: AVG()
Purpose: Average

Function: MAX()
Purpose: Highest value

Function: MIN()
Purpose: Lowest value

✅ Example
SELECT AVG(salary)
FROM employees;

🔹 8. GROUP BY ⭐
Used to group data.
SELECT department, AVG(salary)
FROM employees
GROUP BY department;

🔹 9. Why SQL is Important?
✔ Most asked interview skill
✔ Used daily by analysts & data scientists
✔ Essential for working with databases

🎯 Today’s Goal
✔ Learn SELECT queries
✔ Filter using WHERE
✔ Use aggregate functions
✔ Understand GROUP BY

👉 SQL Resources: https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v 🗄️🔥

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