SQL appears in 58.6% of Stack Overflow survey responses—on par with Python—and shows up in roughly 45% of U.S. tech job postings that require a programming language (Stack Overflow 2025 Technology). Developers dismiss it; employers do not.
These five questions echo themes Indeed groups for database and SQL interviews: query design, performance, integrity, and safe operational practice (Indeed: Database administrator interview questions).
1. “Walk me through a query that joined more tables than you expected. How did you keep it correct?”
Strong candidates explain join keys, cardinality surprises, and how they verified row counts. Weak answers hand-wave “the ORM did it.”
2. “When would you add an index—and when would you avoid one?”
Indeed’s database guides emphasize performance tradeoffs. Listen for read vs write cost, selective columns, and measuring before guessing.
3. “How do you enforce data integrity when application code and the database both touch the same tables?”
You want constraints, transactions, idempotent migrations, and clear ownership—not hope and manual fixes.
4. “Tell me about a slow query you fixed. What did you measure first?”
Good answers start with EXPLAIN, wait stats, or ORM logging—not random index sprawl. They name the bottleneck they found.
5. “How do you ship a schema change on a table with millions of rows without an outage?”
Operational judgment matters for SQL developers on product teams. Strong candidates mention expand/contract migrations, backfills, locks, and rollback plans.
Turn answers into comparable evidence
Capture one join story, one indexing decision, one integrity rule, and one tuning example per finalist. Facts beat dialect trivia.
One scorecard for every finalist
Use the same five questions for each candidate for this opening. Consistent questions support consistent evaluation, which aligns with EEOC guidance for employers to apply the same standards to applicants for the same position (EEOC).
Use Canvider JobCraft to spell out SQL dialect and data volume in the JD, InterviewGen for gap-based follow-ups, and DecisionHelper to compare finalists on the criteria you published.
Next step: Explore InterviewGen and DecisionHelper, then get started free.