SQL task 2: count and display surnames by groups (GROUP BY, COUNT, HAVING).

To count and display surnames that occur more than once (i.e., duplicate surnames), you can use the following SQL query:

SELECT last_name, COUNT(*) as count
FROM Employee
GROUP BY last_name
HAVING COUNT(*) > 1;

Here:

• GROUP BY last_name groups records by surname.
• COUNT(*) counts the number of employees with each surname.
• HAVING COUNT(*) > 1 filters groups where the surname appears more than once.

As a result, you will get a list of surnames and the number of employees with those surnames that are repeated.