为什么这行得通
SELECT DISTINCT FIRSTNAME, LASTNAME
FROM books, CUSTOMERS, orders, orderitems
WHERE STATE IN('FL ', 'GA')
GROUP BY orders.order#, firstname, lastname
HAVING SUM(retail*quantity) > 80
但是什么时候firstname, lastname
从group by
它中删除呢?
ORA-00979: 不是 GROUP BY 表达式