Aggregate functions in SQL
Aggregate functions enable us to return data about the data that a table holds. For example the sum of a given column or its average.
Count return with custom variable
SELECT COUNT(*) AS total_sales
FROM SALES
Sum
SELECT SUM(price) as total_value
FROM sales
Average
SELECT AVG(price) as average_income
FROM sales
Applying aggregate function with sorting applied
SELECT COUNT(*) AS total_sales
FROM sales
GROUP BY employee_id