A data analyst receives a request for the current employee head count and runs the following SQL statement: SELECT COUNT(EMPLOYEE_ID) FROM JOBS. The returned head count is higher than expected because employees can have multiple jobs. Which of the following should return an accurate employee head count?

• A. SELECT JOB_TYPE, COUNT DISTINCT(EMPLOYEE_ID) FROM JOBS
• B. SELECT DISTINCT COUNT(EMPLOYEE_ID) FROM JOBS
• C. SELECT JOB_TYPE, COUNT(DISTINCT EMPLOYEE_ID) FROM JOBS
• D. SELECT COUNT(DISTINCT EMPLOYEE_ID) FROM JOBS

Answer: (D)

Counting unique employees is the right approach when a person can appear in multiple job records. COUNT counts rows, and if an employee has multiple jobs, that one person would be counted multiple times. Using COUNT(DISTINCT EMPLOYEE_ID) collapses all rows for the same employee into a single count, giving the true headcount.

If you grouped by job type, you’d get a separate count for each type rather than the overall total. If you tried a form of COUNT with DISTINCT in a way that doesn’t aggregate across all rows, you’d end up with either per-group counts or an invalid/simplified result, not the single overall headcount.