What is the safe way to update production data if data found inconsistent

I am in a small company and require to fix a bunch of data in production which are inconsistent. I have written the script to handle the fix. I understand that writing sql to fix data is way more risky than working on fixes normal front end or backend code. For front end or back end, we can write thousands of test code to automatically test result or even little bug the affect might not be as dramatic. How do you guys fix the data in production normally if many data was inconsistent? Are there any method or strategy which can reduce the risk