Which comparison operators exist?
Assesses fundamental understanding of SQL & Databases conventions, runtime behavior, and memory/performance considerations.
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Relational SQL engines provide a rich set of comparison operators evaluated in WHERE and HAVING clauses:
| Operator | Meaning | Example |
| :--- | :--- | :--- |
| = | Equal to | status = 'active' |
| != or <> | Not equal to | role <> 'admin' |
| > / < | Greater than / Less than | salary > 75000 |
| >= / <= | Greater or equal / Less or equal | age >= 21 |
| BETWEEN | Inclusive range check | price BETWEEN 10 AND 50 |
| IN | Matches any value in a list | status IN ('new', 'pending') |
| LIKE | Wildcard string pattern matching | email LIKE '%@gmail.com' |
| IS NULL / IS NOT NULL | Null identity checks | deleted_at IS NULL |
| <=> (MySQL) | NULL-safe equality operator | a <=> b |
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.