**Add with default**: ALTER TABLE t ADD COLUMN new_col INT DEFAULT 0; existing rows get default; no full scan in most systems. **Add at end**: Avoids rewriting. **NOT NULL**: May require backfill; add as nullable first, backfill, then alter to NOT NULL. **Backfill**: In batches...
This easy-level SQL question appears frequently in data engineering interviews at companies like Capco. While less common, it tests deeper understanding that distinguishes strong candidates.
Start by clearly defining the core concept being asked about. Interviewers want to see that you understand the fundamentals before diving into implementation details. Structure your answer with a definition, then explain the practical application with a concise example.
Add with default: ALTER TABLE t ADD COLUMN new_col INT DEFAULT 0; existing rows get default; no full scan in most systems. Add at end: Avoids rewriting. NOT NULL: May require backfill; add as nullable first, backfill, then alter to NOT NULL. Backfill: In batches if default not sufficient. Zero-downtime: Additive only; avoid dropping/renaming in same release.
This answer is partially locked
Unlock the full expert answer with code examples and trade-offs
Practice real interviews with AI feedback, track progress, and get interview-ready faster.
Pro starts at $24/mo - cancel anytime
Get the most asked SQL questions with expert answers. Instant download.
No spam. Unsubscribe anytime.
Paste your answer and get instant AI feedback with a FAANG-level improved version.
Analyze My Answer — FreeAccording to DataEngPrep.tech, this is one of the most frequently asked SQL interview questions, reported at 1 company. DataEngPrep.tech maintains a curated database of 1,863+ real data engineering interview questions across 7 categories, verified by industry professionals.