Auto-increment int column BUT also allow manual input? Can't use primary key

Question

Our team is developing a new system for some organization. We have a Client table:

Id (PK), int, not null
NoClient, int, not null

The organization often refers to the Client by its number NoClient . Slowly, clients from the old system will be migrated (manually) to the new system.

NoClient should be auto-increment (for new clients | feature of the new system) while allowing manual input (for existing clients) and not cause collisions later.

Visually, from the point of view of the auto-increment column:

..., 9998, 9999, (used), 10001, 10002

Any idea on how to leverage SQL Server 2005 (or Entity Framework) to solve that problem?

Will likely have to create a seed table and use stored procedures (logic embedded) unless there's a better way to do this...

Answer 1

您可以尝试SET IDENTITY_INSERT ON

Answer 2

Your question was not very clear.

Have a bool column active. Load all existing with the column false. Then just turn it on when the customer is migrated.

As for finding holes.

select min(tb1.PK) + 1 
from table tb1 
left outer join table tb2 
on tb2.pk = tb1.pk + 1 
where tb2.pk is null