Updating data is more complex than inserting it because you must precisely target the correct records while maintaining data integrity.
1The WHERE Clause Trap
Before executing any UPDATE, run it as a SELECT * FROM table WHERE ... first. If the SELECT returns 1 row, your UPDATE will affect 1 row. If it returns 1,000,000 rows... don't run that UPDATE!
2Updating Multiple Columns
Efficiency is key. Updating 5 columns in one query is much faster than running 5 separate queries. It also ensures that either all changes happen or none of them do (atomicity).
3Safe Mode & Transactions
Professional developers often wrap UPDATEs in 'Transactions'. This allows you to 'Rollback' (undo) the change if you realize something went wrong before final confirmation.
