SQL interview question: Conditional Count With SUM and CASE
Conditional Counting with SUM+CASE
Management wants a single-row summary showing employee counts by salary range without multiple queries.
Count employees in each tier in one query using SUM(CASE WHEN...).
Return high_earners (>120k), mid_earners (70k-120k), and low_earners (<70k).
Skills: conditional aggregation pattern
Tables
employees 37 rows
- id integer PK
- first_name text
- last_name text
- email text
- department_id integer → departments
- salary integer
- hire_date text
- manager_id integer → employees
- title text
| id | first_name | last_name | department_id | salary | hire_date | manager_id | title | |
|---|---|---|---|---|---|---|---|---|
| 1 | Alice | Chen | [email protected] | 1 | 250000 | 2015-01-15 | NULL | CEO |
| 2 | Robert | Martinez | [email protected] | 2 | 180000 | 2016-03-20 | NULL | CEO |
| 3 | Sarah | Johnson | [email protected] | 1 | 150000 | 2017-06-10 | 1 | VP Engineering |