13 which statement about multiple column subquery is true?
A.A pairwise comparison produces a cross product
B. A nonpairwise comparison produces a cross product
请问:
what is "pairwise comparison"
and "cross product"
最好能给个例子!!
谢谢!
感激不尽!
SELECT
ordid, prodid, qty
FROM
item
WHERE
prodid IN(SELECT prodid
FROM item
WHERE ordid = 605)
AND
qtyIN(SELECT qty
FROM item
WHERE ordid = 605)
AND ordid605;
Display the order number, product number, and quantity of any item in which the product number and quantity match any product number and any quantity of an item in order 605.
這個就教材中Nonpairwise Comparison Subquery ~~~
看看應該就了解了！
