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LIMIT & OFFSET: Performance

Module: SQL Fundamentals

**Performance Tips:**

- Always use ORDER BY with LIMIT for consistent results

- Index ORDER BY columns for fast sorting

- Large OFFSET is slow - use keyset pagination instead

- LIMIT with index: Database can stop early

- Without index: Must scan all rows before limiting

**Keyset Pagination (for deep pages):**

Instead of: LIMIT 10 OFFSET 10000

Use: WHERE id > last_seen_id ORDER BY id LIMIT 10

Result: Constant time, no matter how deep

Large OFFSET is slow (scans skipped rows)

Keyset pagination: WHERE id > last_id (constant time)

Index ORDER BY columns for fast sorting

LIMIT with index: Database stops early

Avoid OFFSET > 1000 (use keyset instead)

LIMIT without ORDER BY (unpredictable results)

Large OFFSET values (slow performance)

Not indexing ORDER BY columns

Allowing unlimited page_size (DoS risk)

Not handling empty pages gracefully