How can I use a script to change the auto-increment column of a table to a non-auto-increment column?

-- Create a test table
[Create] Table T1 (ID int identity, a INT)
Go
-- Insert record
Insert T1 values (1)
Go
-- 1. Change the identity column to a normal column.
[Alter] Table T1 add id_temp int
Go
Update T1 set id_temp = ID
[Alter] Table T1 drop column ID
Exec sp_rename n 'T1. id_temp ', N 'id', N 'column'
Insert T1 values (100,9)
Go
-- 2. change a common column to an ID column
[Create] Table t1_temp (ID int, A int identity)
Set identity_insert t1_temp on
Insert t1_temp (ID, a) Select * from T1
Set identity_insert t1_temp off
Drop table T1
Go
Exec sp_rename n 'T1 _ temp ', N 't1'
Insert T1 values (109999)
Go
-- Display the processing result
Select * from T1
/* -- Result:
ID
----------------------------
1 1
100 9
109999 10
--*/
I marked "CREATE" and "alter" to upload data. You only need to delete the test!