What goes wrong.
RUNNING UPDATE OR DELETE WITHOUT A WHERE CLAUSE
Changes or removes every row. No undo.
The prevention is running the SELECT first, with the same condition.
NOT BACKING UP BEFORE A CHANGE
The only undo available, and it takes thirty seconds.
PLAIN SQL SEARCH AND REPLACE ON SERIALISED DATA
Corrupts settings silently. Use a serialisation-aware tool.
IMPORTING OVER EXISTING DATA
Produces duplicate key errors and a mixture. Drop the tables first.
FORGETTING THE PREFIX
The most common configuration error, particularly after a migration.
USING ONE DATABASE USER FOR EVERYTHING
One application's vulnerability exposes all of them.
LEAVING A DUMP IN A PUBLIC DIRECTORY
Anyone guessing the URL takes your entire database, including user accounts.
EDITING WHAT THE APPLICATION SHOULD MANAGE
Leaves related data inconsistent.
IGNORING GROWTH
A database that is mostly bloat, slowing everything, unnoticed for years.
ASSUMING BACKUPS WORK
Untested dumps that turn out to be truncated.
