Employee no in HR system

Question

i am working on an HR system and i want to give each new employee a unique number ,i know that the best way is to use sequence number ,but i want the numbers to be without gaps ,so i use
select max(empno)+1 from employess for update;
is this an efficient way,specically that the lock will not make the system slow since each day the maximume number of new employess will be 5 to 10, and they will be registered from distributed application so i am not taking about thousant of people accessing the system at the same time ,so is this an effient solution????

Answer 1

but the sequence number might give you gaps if after selecting the sequence you want to delete the rowNormally, the sequence would invoked in a database BEFORE INSERT trigger, so the user will have already committed. Do not put this functionality in the front-end. If you need to you can use the RETURNING clause to inform the user of the new EMPNO.
Mind you the SEQUENCE may give you gaps any way; that's the sequince caching works. It still preferable to the MAX(empno)+1 approach for these reasons:
(1) Better performance, especially if you have a lot of employees
(2) Works properly in a multi-user environment (without serialization through locking).
(3) Uniqueness is guarenteed.
Cheers, APC