Count（）返回0而不是NULL

Question

I have read the other questions and the answers don't seem to fix my situation. I have a table of company names and a table of activities associated with those companies.

I need to count the amount of activities in a specified date range, and return 0 if there are none. I also need to get the date of the last activity (even if it outside the specified date range).

I am using a LEFT OUTER JOIN , I have tried ISNULL() (although, how can it check if it's null if it doesn't exist?), I'm not sure where to go from here.

This is what I have:

SELECT       v_rpt_Company.Company_Name, COUNT(DISTINCT SO_Activity.SO_Activity_Recid) as touches, MAX(SO_Activity.Date_Entered) As lasttouch
FROM            v_rpt_Member LEFT OUTER JOIN
                         Company_Team ON v_rpt_Member.Member_RecID = Company_Team.Member_RecID LEFT OUTER JOIN
                         v_rpt_Company ON Company_Team.Company_RecID = v_rpt_Company.Company_RecID LEFT OUTER JOIN
                         SO_Activity ON v_rpt_Company.Company_RecID = SO_Activity.Company_RecID
WHERE        (Company_Team.AcctMgr_Flag = 1) AND (v_rpt_Member.Member_ID = @member) AND ((SO_Activity.Last_Update >= CONVERT(datetime, @date_start, 101)) AND ( SO_Activity.Last_Update <= CONVERT(datetime, @date_end, 101))) 
GROUP BY v_rpt_Company.Company_Name
ORDER BY v_rpt_Company.Company_Name ASC,lasttouch DESC,touches DESC

This is the final answer: (Thanks everyone)

SELECT a.touches, a.name,b.lasttouch

FROM (

 SELECT       v_rpt_Company.Company_Name as name,
COUNT(DISTINCT SO_Activity.SO_Activity_Recid) as touches
FROM   v_rpt_Company  
LEFT OUTER JOIN  Company_Team  ON Company_Team.Company_RecID = v_rpt_Company.Company_RecID AND Company_Team.AcctMgr_Flag = 1
LEFT OUTER JOIN v_rpt_Member ON v_rpt_Member.Member_RecID = Company_Team.Member_RecID  
LEFT OUTER JOIN SO_Activity ON v_rpt_Company.Company_RecID = SO_Activity.Company_RecID AND ((SO_Activity.Last_Update >= CONVERT(datetime, @date_start, 101)) AND ( SO_Activity.Last_Update <= CONVERT(datetime, @date_end, 101))) 
WHERE v_rpt_Member.Member_ID = @member
Group By v_rpt_Company.Company_Name ) As a 

LEFT OUTER JOIN

(SELECT MAX(SO_Activity.Date_Entered) As lasttouch, v_rpt_Company.Company_Name as name

FROM   v_rpt_Company  
LEFT OUTER JOIN  Company_Team  ON Company_Team.Company_RecID = v_rpt_Company.Company_RecID AND Company_Team.AcctMgr_Flag = 1
LEFT OUTER JOIN v_rpt_Member ON v_rpt_Member.Member_RecID = Company_Team.Member_RecID
LEFT OUTER JOIN SO_Activity ON v_rpt_Company.Company_RecID = SO_Activity.Company_RecID

WHERE v_rpt_Member.Member_ID = @member 

GROUP BY v_rpt_Company.Company_Name) as b 

ON a.name = b.name

Answer 1

updated: Try this, start with v_rpt_company because you are trying to group by company name.

 SELECT       v_rpt_Company.Company_Name, 
COUNT(DISTINCT SO_Activity.SO_Activity_Recid) as touches, 
MAX(SO_Activity.Date_Entered) As lasttouch
FROM   v_rpt_Company  
LEFT OUTER JOIN  Company_Team  ON Company_Team.Company_RecID = v_rpt_Company.Company_RecID AND Company_Team.AcctMgr_Flag = 1
LEFT OUTER JOIN v_rpt_Member ON v_rpt_Member.Member_RecID = Company_Team.Member_RecID  
LEFT OUTER JOIN SO_Activity ON v_rpt_Company.Company_RecID = SO_Activity.Company_RecID AND ((SO_Activity.Last_Update >= CONVERT(datetime, @date_start, 101)) AND ( SO_Activity.Last_Update <= CONVERT(datetime, @date_end, 101))) 
WHERE v_rpt_Member.Member_ID = @member 
GROUP BY v_rpt_Company.Company_Name
ORDER BY v_rpt_Company.Company_Name ASC,lasttouch DESC,touches DESC

Answer 2

像这样修改您的计数语句：

COALESCE(COUNT(DISTINCT SO_Activity.SO_Activity_Recid),0)

Answer 3

There are two problems with you query:

1. You have conditions in the WHERE clause that are going to be false when there's no activity for that company (since values from SO_Activity will be null, then conditions will be null too).
2. If the date of last activity can be outside the date range, you need a separate join for that.

Here's the fixed version:

SELECT 
v_rpt_Company.Company_Name, 
ISNULL(COUNT(DISTINCT SO_Activity.SO_Activity_Recid), 0) as touches, 
MAX(SO2.Date_Entered) As lasttouch
FROM v_rpt_Member 
LEFT OUTER JOIN Company_Team ON v_rpt_Member.Member_RecID = Company_Team.Member_RecID
LEFT OUTER JOIN v_rpt_Company ON Company_Team.Company_RecID = v_rpt_Company.Company_RecID 
LEFT OUTER JOIN SO_Activity ON v_rpt_Company.Company_RecID = SO_Activity.Company_RecID
                      AND SO_Activity.Last_Update >= CONVERT(datetime, @date_start, 101) 
                      AND SO_Activity.Last_Update <= CONVERT(datetime, @date_end, 101)
LEFT OUTER JOIN SO_Activity SO2 ON v_rpt_Company.Company_RecID = SO_Activity.Company_RecID
WHERE Company_Team.AcctMgr_Flag = 1 AND v_rpt_Member.Member_ID = @member
GROUP BY v_rpt_Company.Company_Name
ORDER BY v_rpt_Company.Company_Name ASC,lasttouch DESC,touches DESC