Встретился вот такой вот вопрос в тестах, ИМХО, правильный ответ не верен или у меня все еще недопонимания в булевой логике!
You want to display item prices from inventory with these desired results:
1. The price of each item is increased by 25 percent.
2. The original price must be over $25.
3. The item manufacturer number must be 25001 or 25050.
4. The original price when multiplied by 25% equals $4.
You query the database with this SQL statement:
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3.
4.
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SELECT price
FROM inventory
WHERE price * . 25 = 4 . 00
AND manufacturer_id = '25001'
OR manufacturer_id = '25050'
OR price > 25 . 00 ;
How many results are covered by this query?
Only two of the desired results are achieved when the script is executed. Desired result #3 which specifies that the item manufacturer number be 25001 or 25050, and desired result #4 which specifies that the price, when multiplied by 25%, equal $4. The statement does not specify that the price of each item be increased by 25 percent or that the price must be over $25 (since the OR logical operator is used instead of the AND operator).
ИМХО, ответ ни одного! Это условие ведь эквивалентно
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SELECT price
FROM inventory
WHERE (price * . 25 = 4 . 00 AND manufacturer_id = '25001')
OR manufacturer_id = '25050'
OR price > 25 . 00 ;
А это означает что если у некоторго inventory price > 25, то он показан в любом случае, так что требования manufacturer number must be 25001 or 25050 и original price when multiplied by 25% equals $4 тоже не выполнены.
