在 Cognos 中创建左外连接查询

Question

I have the following problem. In one table I have a list of Clients with ID, in another table, I have a list of Calls for those Clients. In the datamodel I have marked relationship 0 to many. 1 client can have 0 or many calls. When I create my query I add Client Id and Client Name from Client Table and then add count from Calls Table. In the filter section, I have a filter on Client id and filter on Date Range on Calls Table.

This way I only get clients that had calls and clients without calls do not appear on in the results. Using SQL I wrote the same query to test results and here is what I found.

Using this query I get both clients that have calls and do not have calls. Count(CallId) returns 0 .

select ct.clientid
,ct.ClientName
,count(cs.callid)
from client ct
left outer join calls cs
on ct.clientid = cs.clientid
and cs.CallRecievedDateTime > '1/1/2012' 
and cs.CallRecievedDateTime < '1/2/2012'
where ct.clientid in (1,2,5)
group by ct.clientid, ct.ClientName

Using this query I only get counts for clients with calls. and clients without calls do not appear in results

select ct.clientid
,ct.ClientName
,count(cs.callid)
from client ct
left outer join calls cs
on ct.clientid = cs.clientid
where ct.clientid in (1,2,5)
and cs.CallRecievedDateTime > '1/1/2012' 
and cs.CallRecievedDateTime < '1/2/2012'
group by ct.clientid, ct.ClientName

I can figure out a way to simulate this in Cognos. I solved this problem by creating additional Cognos queries just for the client and then joining it to count query and then using results to display. I want to know if there a way to do it in 1 COGNOS query.

Please do not post SQL Queries. The first query listed is what I'm trying to do in Cognos Application.

Here is another way to get the same results as the first query

SELECT ClientId,
ClientName,
counts
FROM (SELECT clientid,
ClientName
FROM Client
WHERE clientid in (1,2,5) ) cd
LEFT OUTER JOIN
(SELECT clientid,
COUNT(*) counts
FROM calls cs
WHERE cs.CallRecievedDateTime > '1/1/2012'
AND cs.CallRecievedDateTime < '1/2/2012'
GROUP BY clientid) b
ON cd.clientid = b.clientid

Answer 1

如果您只想要有呼叫的客户端，则必须将left outer join替换为inner join

Answer 2

You should do :

select ct.clientid
,ct.ClientName
,count(cs.callid)
from client ct
left outer join calls cs
on ct.clientid = cs.clientid
where ct.clientid in (1,2,5)
and cs.clientid not in (select ct.clientid from client ct inner join calls cs
on ct.clientid = cs.clientid   and cs.CallRecievedDateTime > '1/1/2012' 
and cs.CallRecievedDateTime < '1/2/2012')
and cs.CallRecievedDateTime > '1/1/2012' 
and cs.CallRecievedDateTime < '1/2/2012'
group by ct.clientid, ct.ClientName