更改SUM返回NULL为零

Question

我有一个存储过程如下：

CREATE PROC [dbo].[Incidents]
(@SiteName varchar(200))
AS
SELECT
(  
    SELECT SUM(i.Logged)  
    FROM tbl_Sites s  
    INNER JOIN tbl_Incidents i  
    ON s.Location = i.Location  
    WHERE s.Sites = @SiteName AND i.[month] = DATEADD(mm, DATEDIFF(mm, 0, GetDate()) -1,0)  
    GROUP BY s.Sites  
)  AS LoggedIncidents

'tbl_Sites contains a list of reported on sites.
'tbl_Incidents contains a generated list of total incidents by site/date (monthly)
'If a site doesn't have any incidents that month it wont be listed.

我遇到的问题是网站本月没有任何事件，因此当我运行此proc时，我得到了为该网站返回的NULL值，但我需要返回0/0才能使用SSRS中的图表。

我尝试过使用coalesce并且无所作为。

    SELECT COALESCE(SUM(c.Logged,0))
    SELECT SUM(ISNULL(c.Logged,0))

有没有办法正确地格式化？

干杯，

背风处

Answer 1

把它放在外面：

SELECT COALESCE(

(  
    SELECT SUM(i.Logged)  
    FROM tbl_Sites s  
    INNER JOIN tbl_Incidents i  
    ON s.Location = i.Location  
    WHERE s.Sites = @SiteName AND i.[month] = DATEADD(mm, DATEDIFF(mm, 0, GetDate()) -1,0)  
    GROUP BY s.Sites  
), 0)  AS LoggedIncidents

如果要返回多行，请将INNER JOIN更改为LEFT JOIN

SELECT COALESCE(SUM(i.Logged),0)
FROM tbl_Sites s  
LEFT JOIN tbl_Incidents i  
ON s.Location = i.Location  
WHERE s.Sites = @SiteName AND i.[month] = DATEADD(mm, DATEDIFF(mm, 0, GetDate()) -1,0)  
GROUP BY s.Sites  

顺便说一下，如果没有保证，不要在聚合函数中放置任何函数或表达式，例如不要把ISNULL，COALESCE放在SUM里面，使用function / expression里面的聚合跛子性能，查询将用表扫描执行

Answer 2

你必须像这样使用ISNULL -

ISNULL(SUM(c.Logged), 0)      

或者，正如迈克尔所说，你可以使用左外连接。

Answer 3

我在Oracle中遇到过这个问题。 Oracle没有ISNULL()函数。但是，我们可以使用NVL()函数来实现相同的结果：

NVL(SUM(c.Logged), 0)

Answer 4

我发现实现这一目标的最简单，最易读的方法是：

CREATE PROC [dbo].[Incidents]
(@SiteName varchar(200))

AS

    SELECT SUM(COALESCE(i.Logged, 0)) AS LoggedIncidents
    FROM tbl_Sites s  
    INNER JOIN tbl_Incidents i  
    ON s.Location = i.Location  
    WHERE s.Sites = @SiteName 
          AND i.[month] = DATEADD(mm, DATEDIFF(mm, 0, GetDate()) -1,0)  
    GROUP BY s.Sites  

Answer 5

您可以将SELECT包装在另一个SELECT中，如下所示：

 CREATE PROC [dbo].[Incidents]
(@SiteName varchar(200))

AS

SELECT COALESCE(TotalIncidents  ,0)
FROM (
  SELECT
  (  
    SELECT SUM(i.Logged) as TotalIncidents  
    FROM tbl_Sites s  
    INNER JOIN tbl_Incidents i  
    ON s.Location = i.Location  
    WHERE s.Sites = @SiteName AND i.[month] = DATEADD(mm, DATEDIFF(mm, 0, GetDate()) -1,0)  
    GROUP BY s.Sites  
  )  AS LoggedIncidents
)

Answer 6

刚遇到这个问题，Kirtan的解决方案对我很有用，但语法有点偏差。我喜欢这样：

ISNULL(SUM(c.Logged), 0)

帖子帮助我解决了我的问题，所以感谢所有。