mysql - 我如何找到销售一种类型但不销售另一种类型的制造商？

Question

我必须：

查找销售个人电脑但不销售笔记本电脑的制造商。

此查询未输出正确结果：

SELECT maker, type FROM product
WHERE type = 'PC' AND type <> 'Laptop'

此输出和正确输出：

此查询的结果集：

SELECT maker, type FROM product

表架构：

即使这个也不起作用：

SELECT maker, type FROM product
WHERE type IN('PC') AND type NOT IN('Laptop')

注意 -type添加只是为了澄清

Answer 1

尝试：

SELECT maker
FROM product
GROUP BY maker
HAVING SUM(CASE WHEN type = 'PC' THEN 1 ELSE 0 END) > 0
   AND SUM(CASE WHEN type = 'Laptop' THEN 1 ELSE 0 END) = 0

Answer 2

有许多奇特的方法可以解决这个问题。在这里，首先想到的是:)

1. 微不足道的解决方案。

   SELECT DISTINCT maker
      FROM Product
        WHERE type = 'PC' AND maker NOT IN (
            SELECT maker
            FROM Product
            WHERE type = 'Laptop')
   

2. 使用JOIN

   SELECT DISTINCT Pr.maker
   FROM Product AS Pr LEFT JOIN Product AS Pr2
       ON Pr.maker = Pr2.maker AND Pr2.type = 'Laptop'
   WHERE Pr.type = 'PC' AND Pr2.maker IS NULL
   

3. 使用EXCEPT.

   SELECT DISTINCT maker
       FROM product AS Pr1
       WHERE type = 'PC'
   EXCEPT
   SELECT DISTINCT Pr2.maker
       FROM product AS Pr2
       WHERE type = 'laptop'
   

4. 使用DISTINCT和NOT EXISTS。

   SELECT DISTINCT maker
   FROM Product AS PcP
   WHERE type = 'PC' AND
         NOT EXISTS (SELECT maker
                     FROM Product
                     WHERE type = 'laptop' AND
                     maker = PcP.maker
                    )
   

5. 使用CASE增量和HAVING。

   SELECT maker
       FROM product
   GROUP BY maker
   HAVING SUM(CASE WHEN type = 'PC' THEN 1 ELSE 0 END) > 0
      AND SUM(CASE WHEN type = 'Laptop' THEN 1 ELSE 0 END) = 0
   

6. 使用DISTINCT和比较子查询

   SELECT DISTINCT maker
   FROM Product AS Pr
   WHERE (SELECT COUNT(1)
          FROM Product AS Pt
          WHERE Pt.type = 'PC' AND Pt.maker = Pr.maker
         ) > 0 
       AND
         (SELECT COUNT(1)
          FROM Product AS Pt2
          WHERE Pt2.type = 'Laptop' AND
          Pt2.maker = Pr.maker
         ) = 0
   

7. 使用HAVING和作弊（HAVING不能包含没有聚合的列，所以我们使用无意义的（在这种情况下）聚合MIN（或MAX- 没关系）

   SELECT maker
       FROM (SELECT DISTINCT maker, type
             FROM Product
             WHERE type IN ('PC', 'Laptop')
            ) AS T
   GROUP BY maker
   HAVING COUNT(*) = 1 AND MIN(type) = 'PC'
   

Answer 3

试试这个 找出销售个人电脑但不销售笔记本电脑的制造商。

SELECT maker , type FROM product
WHERE type = 'PC' AND maker NOT IN 
( SELECT maker FROM product WHERE type = 'laptop' )

Answer 4

select distinct maker 
from product 
where type = 'PC'  
  and maker not in ( select maker from product where type = 'Laptop')

有用

Answer 5

SELECT DISTINCT maker
FROM Product AS pc_product
WHERE type = 'pc' AND 
      NOT EXISTS (SELECT maker 
                  FROM Product
                  WHERE type = 'laptop' AND 
                        maker = pc_product.maker
                  );

Answer 6

我可以建议您尝试修剪 where 子句中的值...可能有一些差事空间，因此完全匹配不会返回所需的结果。

像这样：

SELECT maker , type FROM product
WHERE TRIM(type) = 'PC' AND TRIM(type) <> 'Laptop'

或者，您可以简单地尝试：

SELECT maker , type FROM product
WHERE TRIM(type) = 'PC'

如果笔记本电脑和 PC 是 2 种不同的类型，则只需过滤 PC。

Answer 7

尝试如下；

    Select maker from product where type in('PC','laptop')
    except
    select maker from product where type='laptop'

Answer 8

从 type='PC' 和 maker 不在的产品中选择不同的制造商（从 type='laptop' 的产品中选择制造商）

Answer 9

解决问题的简单方法

Select maker from product
where type = 'PC'
Except
Select maker from product
where type = 'laptop'

Answer 10

select distinct Prd.maker as Maker
from   product as Prd INNER JOIN PC as P
ON     Prd.model = P.model
WHERE NOT EXISTS
(
  SELECT 1 FROM Laptop as L INNER JOIN Product as P
  ON L.model = P.model and Prd.maker = P.maker
)

Answer 11

试试这个查询

SELECT DISTINCT MAKER FROM PRODUCT
WHERE TYPE IN ('PC') AND MAKER NOT IN
(SELECT MAKER FROM PRODUCT WHERE TYPE IN ('LAPTOP'))

Answer 12

select maker from Product where type in('PC')
intersect
select maker from Product where type  in ('PC','Printer')
except
select maker from Product where type='Laptop'