Data Definition Query Question -- Add New Autonumber Field

I am trying to write a Data Definition type query that will add a new
auto-numbered column to an existing table.
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Typically, I would set this up with the following syntax:
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"ALTER Table XXX
ADD Column ItemNo Long;"
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However, I want the ItemNo to actually be an autonumber Long Integer
field. Any advise on how to change up the SQL for this query would be
appreciated. Thanks.