Question

我有以下表格

产品 - 存储为productid ProductRelation - 存储链接的产品ID

DECLARE @Product table(ProductID int)

DECLARE @ProductRelation TABLE (FirstProductID int,SecondProductID int)

INSERT INTO @Product 

SELECT 1
UNION ALL
SELECT 2
UNION ALL
SELECT 3
UNION ALL
SELECT 4
UNION ALL
SELECT 5
UNION ALL
SELECT 6
UNION ALL
SELECT 7
UNION ALL
SELECT 8
UNION ALL
SELECT 9
UNION ALL
SELECT 10

--SELECT * FROM @Product

INSERT INTO @ProductRelation

SELECT 1,2
UNION ALL
SELECT 3,5
UNION ALL
SELECT 2,6
UNION ALL
SELECT 1,4
UNION ALL
SELECT 1,4

--SELECT * FROM @ProductRelation

SELECT ProductID,'Not Linked' AS 'Relation' FROM @Product
UNION
SELECT FirstProductID,'Linked' from @ProductRelation
UNION
SELECT SecondProductID ,'Linked' FROM @ProductRelation

以上查询结果重复ProductID

我想选择不同的ProductID ...如果产品ID之间存在关联，那么它应该显示带有'Linked'的ProductID 如果没有关系，那么ProductID与'Not Linked'

我想要这样的预期结果

ProductID          Relation

1           Linked
2           Linked
3           Linked
4           Linked
5           Linked
6           Linked
7           Not Linked
8           Not Linked
9           Not Linked
10          Not Linked

Answer 1

试试这个：

SELECT
   P.ProductID,
   CASE WHEN COUNT(R.FirstProductID) > 0
        THEN 'Linked'
        ELSE 'Not Linked'
   END Relation
FROM Product P
   LEFT JOIN ProductRelation R
      ON P.ProductID = R.FirstProductID
        OR P.ProductID = R.SecondProductID
GROUP BY P.ProductID

Answer 2

好吧......我喜欢这个机会使用一些非常棒的技巧！

select P.ProductID
,isnull(L.relation,'Not Linked') as relation
from @Product P
left outer join (select U.ProductID, cast('Linked' as varchar(max)) as relation
                from @ProductRelation
                unpivot (ProductID for prod in (FirstProductID,SecondProductID))U
                group by U.ProductID
)L
on L.ProductID = P.ProductID

Answer 3

您可以在SQL Server中使用左连接和CASE WHEN

SELECT DISTINCT 
   ProductID,
   CASE WHEN @ProductRelation.FirstProductId IS NULL THEN 'Not Linked' ELSE 'Linked' END [Status]
FROM @Product 
LEFT JOIN @ProductRelation ON @Product.ProductID = @ProductRelation.FirstProductId
RIGHT JOIN @ProductRelation ON @Product.ProductID = @ProductRelation.SecondProductId

得到明显的结果

3 个答案: