Create identity to create table with data

Normally we can't create the identity in the existing column, it must be created while creating the table. Suppose if you have a data in the table you want to add the identity in the table, we can do it in indirect way as below.

Consider the table as table1 and it contain a column as column1

Now am rename the table1 as table1_new as below

sp_rename 'table1','table1_new'

Now create a new table as table1

create table table1(column1 int primary key identity(1,1))

then turn off identity

set identity_insert table1 on

Now copy all data from old table to new table as below

insert into table1(column1 )

select column1 from table1

Now turnon the identity

set identity_insert table1 off

Find the max value of column

select MAX(column1) from table1

Reseed the identity as below

DBCC CHECKIDENT (table1, RESEED, 220);

Now you can make use of the table along with identity as before