Top Departments by Call Volume

NJM Insurance Group wants to identify which departments handled the most calls during the previous calendar quarter. Write a PostgreSQL query that ranks departments by the number of calls received in that period.

Requirements

1. Define the last quarter as the complete calendar quarter immediately before the anchored reference date of August 29, 2026.
2. Count calls by department, excluding calls outside the last quarter and calls that do not reference a department.
3. Return the top three departments, including department name and call volume.
4. Break ties consistently by ordering department ID ascending after call volume descending.

Output

1. Return one row per selected department with columns department_name and call_volume.
2. Include only calls from April 1 through June 30, 2026. Calls with NULL or unmatched department IDs are excluded.
3. Return the top three departments, ordered by call volume descending and department name ascending.
4. Departments with no qualifying calls remain eligible with a count of zero, but are not expected in the top three.