While the auto identity option is true, a 10-digit IDENTITY column is defined in each new table that is created without specifying either a primary key, a unique constraint, or an IDENTITY column. This IDENTITY column is only created when you issue a create table command, not when you issue a select into. The column is not visible when you select all columns with the select * statement. To retrieve it, you must explicitly mention the column name, SYB_IDENTITY_COL, in the select list.
To set the precision of the automatic IDENTITY column, use the size of auto identity configuration parameter.
Though you can set auto identity to true in tempdb, it is not recognized or used, and temporary tables created there do not automatically include an IDENTITY column.
