Question

我必须：

找到销售PC而非笔记本电脑的制造商。

此查询未输出正确的结果：

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

此输出和正确的输出：

output

此查询的结果集：

SELECT maker, type FROM product

ex2

表架构：

table

即便是这个也不起作用：

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

注意 - 仅为了澄清而添加type

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

试试这个 找出销售PC而不是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 3

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：）

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')

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

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'

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
                 )

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

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

使用HAVING并作弊（HAVING不能包含没有聚合的列，因此我们使用无意义（在本例中）聚合MIN（或{{1 - 无所谓）
```
MAX
```

Answer 4

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

它有效

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...可能存在一些差事空格，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，您可以尝试：

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

如果笔记本电脑和PC是两种单独的类型，那么只需过滤PC。

Answer 7

尝试如下;

num = int(num)

Answer 8

从产品中选择不同的制造商，其中type =＆＃39; PC＆＃39;并且制造商不在（从产品中选择制造商，类型=＆＃39;笔记本电脑＆＃39;）

Answer 9

解决问题的简便方法

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

尝试此查询

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'

我如何找到销售一种类型而不是另一种类型的制造商？

12 个答案: