Question

我有一个以item_Number作为其主键的产品表。每个项目都分配到一个位置，并且每个项目都可以标记为不同的类别。

我想编写一个查询来显示没有类别“小”的item_number。考虑到数据库中有成千上万个项目，需要知道哪些项目以后没有什么小类别。

这里是样本数据集，以供参考和示例

Item_Number      Location   Category
A                East       Big
A                East       Small
A                East       Medium
B                East       Big
B                East       Medium
C                East       Big
C                East       Small
C                East       Medium
D                East       Big
D                East       Medium

这是我的初始代码

select  item_Num, location 
from PRODUCT 
WHERE location  = 'East' and category <> 'Small'

该代码返回

 Item_Number     Location   
    A                East       
    A                East       
    B                East      
    B                East       
    C                East       
    C                East       
    D                East       
    D                East

预期结果应该是

 Item_Number     Location   
    B                East      
    D                East

Answer 1

您可以使用分组：

SELECT item_Num, 'East'  
FROM PRODUCT 
WHERE location  = 'East' 
GROUP BY item_num
HAVING COUNT(CASE WHEN category = 'Small' THEN 1 END) = 0

HAVING子句就像WHERE应用于具有相同item_num的记录的 group 组。该查询的谓词将检查不包含任何category = 'Small'记录的组。

Demo here

Answer 2

使用不存在的相关子查询

select  distinct item_Num, location 
from PRODUCT a
WHERE location  = 'East' and not exists 
  (select 1 from PRODUCT b where a.item_Num=b.item_Num and b.Category='Small' 
      and b.location  = 'East')

或者您可以尝试这个

select  item_Num, location 
from product
WHERE location  = 'East'
group by item_Num, location 
having sum(case when Category='Small' then 1 else 0 end)=0

Answer 3

不存在

select t1.* from PRODUCT t1
where not exists ( select 1 from PRODUCT t2 where t1.Item_Number=t2.Item_Number and Category='Small')
and location='East'

Answer 4

请尝试这个。

SELECT DISTINCT item_Num, location 
FROM PRODUCT 
WHERE location  = 'East' and Item_Number  Not in (SELECT Item_Number FROM PRODUCT  WHERE category ='Small')

SQL查询以显示没有特定记录的项目

4 个答案: