SELECT with NULL Handling
Return employees who do not have a manager.
- NULL handling
- Filtering
Exercise brief
Understand the request
Org design lead The org-chart review starts with employees who do not report to anyone.
Return first_name, last_name, and manager_id for every employee who does not report to a manager (manager_id is NULL).
Return
- Return first_name, last_name, and manager_id.
Constraints
- Filter with IS NULL on manager_id.
Data you will use
Review the relevant tables before deciding how to join, filter, or aggregate them.
employees
first_nameVARCHAR(50)last_nameVARCHAR(50)manager_idINTEGER
Hints, when you need them
Open one clue at a time so you still do the reasoning.
Hint 1
NULL is "unknown" — comparing it with `=` always returns NULL, never true. Use IS NULL / IS NOT NULL instead.
Hint 2
`WHERE manager_id = NULL` returns 0 rows. `WHERE manager_id IS NULL` is what you want.
Hint 3
Project the requested employee fields, then test manager_id with IS NULL.
Verified SQL answer
Attempt the problem first, then compare structure and reasoning—not just syntax.
Reveal solution and explanation
SELECT first_name, last_name, manager_id FROM employees WHERE manager_id IS NULL;Why this works
SQL has three-valued logic: TRUE, FALSE, UNKNOWN (NULL). Equality comparisons against NULL evaluate to UNKNOWN, which WHERE treats as "do not include this row". The IS NULL / IS NOT NULL operators are the only way to test for the NULL state.
Expected result
Use this output to verify values, aliases, ordering, and row count.
| first_name | last_name | manager_id |
|---|---|---|
| John | Smith | NULL |
| Carol | Davis | NULL |
| David | Brown | NULL |
| Emma | Taylor | NULL |
Learn the concepts behind this answer
Strengthen your understanding with these targeted learning topics:
Continue practicing
Build the next SQL skill
WHERE Clause & Filtering
Practice SQL WHERE clauses with realistic boundary, NULL, text, date, exclusion, and production-filtering problems.
Basic SQL Functions
Practice production-oriented string cleanup, numeric transformations, NULL handling, tolerant conversion, and delimiter parsing.
ORDER BY & Sorting
Practice deterministic SQL ordering with tie-breakers, custom priorities, NULL placement, expressions, joined data, aggregates, and portable top-N patterns.
Open the interactive workspace and practice across SQL topics.