Sql-server – How to copy a table with SELECT INTO but ignore the IDENTITY property

identitysql serversql-server-2005

I have a table with identity column say:

create table with_id (
 id int identity(1,1),
 val varchar(30)
);

It's well known, that this

select * into copy_from_with_id_1 from with_id;

results in copy_from_with_id_1 with identity on id too.

The following stack overflow question mentions listing all columns explicitly.

Let's try

select id, val into copy_from_with_id_2 from with_id;

Oops, even in this case id is an identity column.

What I want is a table like

create table without_id (
 id int,
 val varchar(30)
);

Best Answer

From Books Online

The format of new_table is determined by evaluating the expressions in the select list. The columns in new_table are created in the order specified by the select list. Each column in new_table has the same name, data type, nullability, and value as the corresponding expression in the select list. The IDENTITY property of a column is transferred except under the conditions defined in "Working with Identity Columns" in the Remarks section.

Down the page:

When an existing identity column is selected into a new table, the new column inherits the IDENTITY property, unless one of the following conditions is true:

  • The SELECT statement contains a join, GROUP BY clause, or aggregate function.
  • Multiple SELECT statements are joined by using UNION.
  • The identity column is listed more than one time in the select list.
  • The identity column is part of an expression.
  • The identity column is from a remote data source.

If any one of these conditions is true, the column is created NOT NULL instead of inheriting the IDENTITY property. If an identity column is required in the new table but such a column is not available, or you want a seed or increment value that is different than the source identity column, define the column in the select list using the IDENTITY function. See "Creating an identity column using the IDENTITY function" in the Examples section below.

So... you could theoretically get away with:

select id, val 
into copy_from_with_id_2 
from with_id

union all

select 0, 'test_row' 
where 1 = 0;

It would be important to comment this code to explain it, lest it be removed the next time someone looks at it.

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