โ
SQL for Data Science ๐๏ธ๐
๐ 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.
๐น 1. What is SQL?
SQL = Structured Query Language
๐ Used to:
โ Store data
โ Retrieve data
โ Filter data
โ Analyze data
๐ฅ 2. Common Database Systems
โ MySQL
โ PostgreSQL
โ SQLite
โ Microsoft SQL Server
๐น 3. Basic SQL Query
โ
SELECT Statement
Used to retrieve data from a table.
SELECT * FROM employees;
๐ ** means all columns.
๐น 4. Select Specific Columns
SELECT name, salary FROM employees;
๐น 5. WHERE Clause โญ
Used for filtering data.
SELECT * FROM employees
WHERE salary > 50000;
๐น 6. ORDER BY
Sort data.
SELECT * FROM employees
ORDER BY salary DESC;
โ ASC โ Ascending
โ DESC โ Descending
๐น 7. Aggregate Functions โญ
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
โ
Example
SELECT AVG(salary)
FROM employees;
๐น 8. GROUP BY โญ
Used to group data.
SELECT department, AVG(salary)
FROM employees
GROUP BY department;
๐น 9. Why SQL is Important?
โ Most asked interview skill
โ Used daily by analysts & data scientists
โ Essential for working with databases
๐ฏ Todayโs Goal
โ Learn SELECT queries
โ Filter using WHERE
โ Use aggregate functions
โ Understand GROUP BY
๐ SQL Resources: https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v ๐๏ธ๐ฅ
๐ฌ Tap โค๏ธ for more!
1August 28, 2026 274 1
