Facing problem Increamenting by one in Sql Server Field whose data type in character

The idea in database design, is to keep each data element separate. And each element has its own datatype, constraints and rules. That IP2 is not one field, but two. Same with XXXnnn or whatever. It is incorrect, and it will severely limit your ability to use the data, and use database features and facilities.

Break it up into two discrete data items:

column_1 CHAR(1)
column_2 INTEGER

Then set AUTOINCREMENT on column_2

And yes, your Primary Key can be (column_1, column_2), so you have not lost whatever meaning IP2 has for you.

Try this

CREATE TABLE dbo.Demo(ID INT IDENTITY PRIMARY KEY,
                      IDwithChar AS 'IP' + RIGHT('-' + CAST(ID AS VARCHAR(10)), 6) PERSISTED )

Hope it helps J