I discover that if no database defined in "loopback...po_01" in "create existing table" command will refer the user id's default database instead of current database.

Normally, ".." will refer current database.

e.g a user A's default database after login is db_A and it can access & create objects in db_A & db_B.

User A create a sp po_01 & "create existing table .... loopback...po_01" in db_B.

Sybase return
Server Message: Number 2812, Severity 16
Server 'loopback', Line 1:
Stored procedure 'po_01' not found. Specify owner.objectname or use sp_help to check whether the object exists (sp_help may produce lots of output).

But it can if do the same in db_A. ...

any ways can "loopback..." to refer current database instead of login database....