SQL 服务器：添加 LEFT JOIN 后更改字段的总和

Question

我有一个这样的示例查询：

;WITH view1 AS (
    SELECT 1 AS id, 1 AS pId, 'a' AS pName, 1 AS kind 
    UNION ALL SELECT 2, 1, 'a', 2 
    UNION ALL SELECT 3, 1, 'a', 1 
    UNION ALL SELECT 4, 2, 'b', 2 
    UNION ALL SELECT 5, 2, 'b', 2 
    UNION ALL SELECT 6, 2, 'b', 1 
), view2 AS (
    SELECT 1 AS id, 1 AS pId, 'a' AS pName, 5 AS price
    UNION ALL SELECT 3, 3, 'c', 3 
    UNION ALL SELECT 6, 2, 'b', 3 
)   
SELECT 
    ISNULL(v2.pId, v1.pId) AS pId,
    ISNULL(v2.pName, v1.pName) AS pName,
    SUM(CASE v1.kind WHEN 1 THEN 1 ELSE 0 END) AS countKind1,
    SUM(v2.price) AS sumPrice
FROM 
    view1 v1
    LEFT OUTER JOIN
    view2 v2 ON v1.id = v2.id
GROUP BY
    ISNULL(v2.pId, v1.pId),
    ISNULL(v2.pName, v1.pName)

其结果是：

pId | pName | countKind1 | sumPrice
----+-------+------------+-----------
1   | a     | 1          | 5
2   | b     | 1          | 3 
3   | c     | 1          | 3

但是我在添加 ISNULLs 和 sumPrice 之后想要这个结果：

pId | pName | countKind1 | sumPrice
----+-------+------------+-----------
1   | a     | 2          | 5
2   | b     | 1          | 3 
3   | c     | 0          | 3

Answer 1

您的查询看起来有点奇怪。我可以创建几种获得所需结果的方法，但我不确定您的数据背后的含义是什么。一般来说，我总是建议您尽早对数据进行分组，因此您可能可以对 view1 进行分组，然后按 pId.

加入

这里是给出结果的查询

;WITH view1 AS (
    SELECT 1 AS id, 1 AS pId, 'a' AS pName, 1 AS kind 
    UNION ALL SELECT 2, 1, 'a', 2 
    UNION ALL SELECT 3, 1, 'a', 1 
    UNION ALL SELECT 4, 2, 'b', 2 
    UNION ALL SELECT 5, 2, 'b', 2 
    UNION ALL SELECT 6, 2, 'b', 1 
), view2 AS (
    SELECT 1 AS id, 1 AS pId, 'a' AS pName, 5 AS price
    UNION ALL SELECT 3, 3, 'c', 3 
    UNION ALL SELECT 6, 2, 'b', 3 
), cte1 as (
SELECT 
    ISNULL(v2.pId, v1.pId) AS pId,
    ISNULL(v2.pName, v1.pName) AS pName,
    SUM(v2.price) AS sumPrice
FROM 
    view1 v1
    LEFT OUTER JOIN
    view2 v2 ON v1.id = v2.id
GROUP BY
    ISNULL(v2.pId, v1.pId),
    ISNULL(v2.pName, v1.pName)
), cte2 as (
    select pName, sum(case when kind = 1 then 1 else 0 end) as countKind1
    from view1
    group by pName
)
select
    c1.pId,
    c1.pName,
    isnull(c2.countKind1, 0) as countKind1,
    c1.sumPrice
from cte1 as c1
    left outer join cte2 as c2 on c2.pName = c1.pName

sql fiddle demo

Answer 2

根据@Roman 的评论，您需要加入 pID。您还需要将 JOIN 更改为 FULL OUTER 连接，因为 view1 没有 'c' 最后，SUM(Price) 看起来不对 - 如果这是每 'each' 的价格，您需要使用不同的聚合，例如 Max:

;WITH view1 AS (
    SELECT 1 AS id, 1 AS pId, 'a' AS pName, 1 AS kind 
    UNION ALL SELECT 2, 1, 'a', 2 
    UNION ALL SELECT 3, 1, 'a', 1 
    UNION ALL SELECT 4, 2, 'b', 2 
    UNION ALL SELECT 5, 2, 'b', 2 
    UNION ALL SELECT 6, 2, 'b', 1 
), view2 AS (
    SELECT 1 AS id, 1 AS pId, 'a' AS pName, 5 AS price
    UNION ALL SELECT 3, 3, 'c', 3 
    UNION ALL SELECT 6, 2, 'b', 3 
)   
SELECT 
    ISNULL(v2.pId, v1.pId) AS pId,
    ISNULL(v2.pName, v1.pName) AS pName,
    SUM(CASE WHEN v1.kind = 1 THEN 1 ELSE 0 END) AS countKind1,
    MAX(v2.price) AS maxPrice
FROM 
    view1 v1
    FULL OUTER JOIN
    view2 v2 ON v1.pid = v2.pid
GROUP BY
    ISNULL(v2.pId, v1.pId),
    ISNULL(v2.pName, v1.pName)

SqlFiddle here

Answer 3

我找到了使用内联的方法 select:

SELECT 
    ISNULL(v2.pId, v1.pId) AS pId,
    ISNULL(v2.pName, v1.pName) AS pName,
    (SELECT COUNT(*) FROM view1 vi WHERE vi.kind = 1 AND vi.pId = ISNULL(v2.pId, v1.pId)) AS countKind1,
    SUM(v2.price) AS sumPrice
FROM 
    view1 v1
    LEFT OUTER JOIN
    view2 v2 ON v1.id = v2.id
GROUP BY
    ISNULL(v2.pId, v1.pId),
    ISNULL(v2.pName, v1.pName)

还有这个：

SELECT 
    ISNULL(v2.pId, v1.pId) AS pId,
    ISNULL(v2.pName, v1.pName) AS pName,
    ISNULL(tc.Counts, 0) AS countKind1,
    SUM(v2.price) AS sumPrice
FROM 
    view1 v1
    LEFT OUTER JOIN
    view2 v2 ON v1.id = v2.id
    LEFT OUTER JOIN
    (SELECT vi.pId, COUNT(*) Counts FROM view1 vi WHERE vi.kind = 1 GROUP BY vi.pId) AS tc ON tc.pId = ISNULL(v2.pId, v1.pId)
GROUP BY
    ISNULL(v2.pId, v1.pId),
    ISNULL(v2.pName, v1.pName),
    tc.Counts

SQL 服务器：添加 LEFT JOIN 后更改字段的总和

SQL Server : Sum over a field changed after adding a LEFT JOIN

sql

sql-server

left-join