5.4. Understand Procedural Integrity
In most cases, procedural integrity should be a last resort. In almost every case, it is higher in overhead than its constraint counterparts There are also a few procedural options, namely rules and defaults that are scheduled to be obsoleted in SQL Server. There are four primary procedural options for implementing integrity:
The Rule is a special stored procedure that defines a data restriction, much like a check constraint. Microsoft has announced that it plans to remove the Rule procedure type in a future version of SQL Server. It is provided now only for compatibility. It is our strong recommendation that you do not do any new development using the procedural Rule. Instead, use the check constraint. ...