What's your #1 way to be careful with a live database?

For my customer I occasionally do work in their live database in order to fix a problem they have created for themselves, or in order to fix bad data that my product's bugs created. Much like Unix root access, it's just dangerous. What lessons should I learn ahead of time?

What is the #1 thing you do to be careful about operating on live data?

Make your changes to a copy, and when you're satisfied, then apply the fix to live.

Always make sure your UPDATEs and DELETEs have the proper WHERE clause.

Make sure you specify a where clause when deleting records.

always test any queries beyond select on development data first to ensure it has the correct impact.

Backup or dump the database before starting.

To add on to what @[Wayne][1] said, write your `WHERE` before the table name in a `DELETE` or `UPDATE` statement.


[1]:

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BACK UP YOUR DATA. Learned that one the hard way working with customer databases on a regular basis.

Maybe consider not using any deletes or drops at all. Or maybe reduce the user permissions so that only a special DB user can delete/drop things.

Always add a using clause.