Once defined, the business rule is physically implemented and can not be bypassed. This effectively minimizes the amount of code that must be written by the programming staff. With the significant application backlog within most organizations, this can be the most crucial reason to utilize check constraints. Check constraints provide better data integrity. When business rules are enforced using application programming logic instead, the rules can not be checked during ad hoc processes.
Check constraints promote consistency.
Because they are implemented once, in the table DDL, each constraint is always enforced. Constraints written in application logic, on the other hand, must be executed by each program that modifies the data to which the constraint applies. This can cause code duplication and inconsistent maintenance resulting in inaccurate business rule support. Typically check constraints coded in DDL will outperform the corresponding application code. The overall impact of check constraints will be to increase application development productivity.