SQL Server数据库中外键强制约束的好处是什么，什么时候设置外键非强制约束？（转载）
Sql Server: What is the benefit of using “Enforce foreign key constraint” when it's set to “NO”?
问
I know the purpose of "Enforce foreign key constraint" in RDBMS. But is there any benefit when it's set to "NO" ?
答
In normal production, this setting should never be set to NO.
But: when you're developing, or restructuring a database, or when you do e.g. a large bulk load of data that you'll need to "sanitize" (clean up), then it can make sense to turn off foreign key constraints to allow "non-valid" data to be loaded into a table. Of course, as I said - you shouldn't keep that setting turned off for a long period of time - you should then proceed to clean up the data, either delete those rows that are in violation of the FK constraint, or update their values so they match a parent row.
So again: in "normal" production mode, this setting should never be NO - but for specific tasks, it might help get the job done more easily. Use it with caution, and always turn the FK constraints back on as soon as you can!
