[AlisdairO]

Table User: userid, etc

Table Resources: resourceid, userid, etc

If I want to restrict deletion of a user to only be possible after all the resources are deleted, I'm forced into using higher-than-default isolation levels in most DBs. This has significant performance implications. It's also much easier to make a mistake - for example, if when creating a resource I check that the user exists prior to starting the transaction, then start the tran, then do the work, it will allow insertion of data into a nonexistent user.

[edf13]

Add your user check as a where clause on the resources insert?

[AlisdairO]

Can you give an example? I’m not aware of a mechanism like that that will protect you from concurrency artifacts reliably - certainly not a general one.