อัปเดตระเบียนเดิมอย่างปลอดภัย

Updating means changing an existing row, not making a new one. The trick is to load the record first, then edit it. ✏️

Always fetch the target row by its id before touching it. get_or_404() loads it or stops with a clean 404.

Once loaded, just reassign its attributes. SQLAlchemy notices the change and marks the object as dirty for you.

Updates usually carry the new data in the request body. Parse it with get_json() before applying anything.

Only overwrite fields the client actually sent. Using get() with a fallback avoids wiping values to None by accident.

No add() is needed for an existing row. A single commit() flushes your edits to the database.

Use PUT when the client sends the whole object and PATCH when it sends only the fields it wants to change.

Check incoming values before you commit. Reject bad data with a 400 so you never persist a broken record.

If the commit raises, call rollback() to discard the half-applied edit and leave the row exactly as it was.

A good update reply sends back the fresh record with status 200, so the client sees the saved result.

The whole update flow is three beats: load the row, change its attributes, then commit. No new object ever appears.

You changed a loaded object's attribute. What must happen for the edit to stick?

You load with get_or_404, apply only sent fields, validate, then commit, rolling back on errors. Safe updates unlocked! 🎉