MySQLのトリガ。

Question

は、私が唯一のラップトップを作る製品のメーカーを見つけようとしています例に答える必要はありませんPCの

Relations: 
Product(maker, model, type) 
Laptop(Model, price, speed, ram, hd, screen) 
PC(model, price, speed, ram, hd) 
Printer(model,price, color, price) 

私はそれを取る

(SELECT maker, type 
FROM product WHERE type = 'laptop') 
DIFFERENCE 
(SELECT maker, type 
FROM product WHERE type = 'pc'); 

は差の操作は、MySQLに存在しないを試してみましたか？

Answer 1

select maker, type from product 
where type='laptop' and 
maker not in (select maker from product where type = 'pc') 

Answer 2

SELECT p.maker, p.type 
    FROM product p 
    WHERE p.type = 'laptop' 
    AND NOT EXISTS ( 
     SELECT p2.maker, p2.type 
     FROM table p2 
     WHERE p2.type = 'pc' 
     AND p2.maker = p1.maker 
    ) 

Answer 3

SELECT maker, type FROM product WHERE type = 'laptop' AND type != 'pc';

Answer 4

SELECT 
    p1.maker, 
    p1.type 
FROM 
    product p1 
    LEFT JOIN product p2 ON p2.maker = p1.maker AND p2.type = 'pc' 
WHERE 
    p1.type = 'laptop' 
    p2.maker IS NULL 

Answer 5

SELECT `maker`, `type` FROM `product` WHERE `type` = 'laptop' AND `maker` NOT IN 
       (SELECT `maker`, `type` FROM `product` WHERE `type` = 'pc');