Database / SQLite Interview questions

What is an UPSERT in SQLite (INSERT... ON CONFLICT)?

An upsert inserts a new row, or updates an existing one instead if the insert would violate a uniqueness constraint — a single statement covering both the "create" and "update" case, avoiding a separate check-then-insert-or-update sequence in application code.

INSERT INTO person (id, name, visit_count)
VALUES (1, 'Ada', 1)
ON CONFLICT(id) DO UPDATE SET visit_count = visit_count + 1;

ON CONFLICT(column) DO UPDATE SET ... specifies exactly what to do when a conflicting row already exists, and can reference the conflicting existing row's values via excluded.column for the values that were about to be inserted. There's also a simpler DO NOTHING variant when you just want to silently skip the insert on conflict rather than updating anything.

Take quiz

What problem does INSERT ... ON CONFLICT DO UPDATE solve? It prevents any duplicate rows from ever existing, silently

✗ Not quite. Try again.

It combines insert-or-update into a single statement instead of a separate check-then-act sequence

✓ Correct! Well done.

It only works for numeric columns

✗ Not quite. Try again.

What does ON CONFLICT DO NOTHING do? Silently skips the insert if a conflict occurs, without updating anything

✓ Correct! Well done.

Always raises an error on conflict

✗ Not quite. Try again.

Deletes the conflicting existing row

✗ Not quite. Try again.

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Database / SQLite Interview questions

What is an UPSERT in SQLite (INSERT... ON CONFLICT)?

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