Mastering SQL is essential for analyzing, filtering, and summarizing large datasets. Here's a quick guide with real-world use cases:
1๏ธโฃ SELECT, WHERE, AND, OR
Filter specific rows from your data.
SELECT name, age
FROM employees
WHERE department = 'Sales' AND age > 30;
2๏ธโฃ ORDER BY & LIMIT
Sort and limit your results.
SELECT name, salary
FROM employees
ORDER BY salary DESC
LIMIT 5;
โถ๏ธ Top 5 highest salaries
3๏ธโฃ GROUP BY + Aggregates (SUM, AVG, COUNT)
Summarize data by groups.
SELECT department, AVG(salary) AS avg_salary
FROM employees
GROUP BY department;
4๏ธโฃ HAVING
Filter grouped data (use after GROUP BY).
SELECT department, COUNT(*) AS emp_count
FROM employees
GROUP BY department
HAVING emp_count > 10;
5๏ธโฃ JOINs
Combine data from multiple tables.
SELECT e.name, d.name AS dept_name
FROM employees e
JOIN departments d ON e.dept_id = d.id;
6๏ธโฃ CASE Statements
Create conditional logic inside queries.
SELECT name,
CASE
WHEN salary > 70000 THEN 'High'
WHEN salary > 40000 THEN 'Medium'
ELSE 'Low'
END AS salary_band
FROM employees;
7๏ธโฃ DATE Functions
Analyze trends over time.
SELECT MONTH(join_date) AS join_month, COUNT(*)
FROM employees
GROUP BY join_month;
8๏ธโฃ Subqueries
Nested queries for advanced filters.
SELECT name, salary
FROM employees
WHERE salary > (SELECT AVG(salary) FROM employees);
9๏ธโฃ Window Functions (Advanced)
SELECT name, department, salary,
RANK() OVER(PARTITION BY department ORDER BY salary DESC) AS dept_rank
FROM employees;
โถ๏ธ Rank employees within each department
๐ก Used In:
โข Marketing: campaign ROI, customer segments
โข Sales: top performers, revenue by region
โข HR: attrition trends, headcount by dept
โข Finance: profit margins, cost control
SQL For Data Analytics: https://whatsapp.com/channel/0029Vb6hJmM9hXFCWNtQX944
๐ฌ Tap โค๏ธ for more