Find employees who are working on more than two projects.

To find employees assigned to more than two projects, you can use a GROUP BY with a HAVING clause. Assuming you have an employees table (employees) and a junction table (employee_projects) that links employees to projects, the query would look like this:

SELECT e.employee_id,

   e.first_name,
   e.last_name

FROM employees e

JOIN employee_projects ep ON e.employee_id = ep.employee_id

GROUP BY e.employee_id, e.first_name, e.last_name

HAVING COUNT(DISTINCT ep.project_id) > 2;

Explanation:

• The JOIN brings together each employee with their project assignments.
• GROUP BY aggregates rows per employee.
• COUNT(DISTINCT ep.project_id) counts unique projects for each employee.
• HAVING filters groups where the count exceeds 2.

Complexity: The query scans the employee_projects table once (O(n)) and performs a hash/grouping operation. The overall time is linear in the number of rows in employee_projects, and the memory usage is proportional to the number of distinct employees. This is efficient for typical relational databases and scales well with large datasets.