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http://docs.oracle.com/cd/E11882_01/server.112/e10592/statements_7002.htm#i2095331

http://asktom.oracle.com/pls/asktom/f?p=100:11:0%3a%3a%3a%3aP11_QUESTION_ID:48812348054

CREATE GLOBAL TEMPORARY TABLE today_sales
   ONCOMMIT PRESERVE ROWS 
   ASSELECT*FROM orders WHERE order_date = SYSDATE;