Implementing delete feature in ios apps: How to make sure deleting data doesn't mess up the reports

For sql based data

If user has made no transaction. delete him,remove him.
But if he made purchase and his data(user_id) is saved on multiple tables,then

• make deleted user table. whenever you delete make the obfuscated user data in this table. so the app,cms doesn't break. Also let your user know that for legal purposes some data needs to be retained.

For non sql.

Obfuscate the users data, and insert the user's data as key(eg owner) where the user id was used. Basically insert it as sub document.

Maybe this is not the best solution, for us it worked. how did you guys fixed it