Why are COUNT and GROUP BY used?

COUNT and GROUP BY are key constructs in SQL for data analysis and aggregation.

• COUNT is a function that counts the number of rows or values in a column. For example, to find out how many records are in a table:

SELECT COUNT(*) FROM employees;

• GROUP BY is a statement that groups rows by the value of one or more columns. This allows applying aggregate functions (like COUNT, SUM, AVG) to each group separately.

Example: count the number of employees in each department:

SELECT department, COUNT(*) AS employee_count
FROM employees
GROUP BY department;

This will give you a list of departments with the number of employees in each.