How to Optimize this SQL Query? - sql

Question

I have 3 tables:
CRSTasks (ID,parentID)
CRSTaskReceivers (ID,tskID,receiverID)
UserNames (id,name)
...relation between CRSTasks and CRSTaskReceivers one-to-many
between UserNames and CRSTaskReceivers one-to-one
tasks
ID parent
1 null
10 1
50 1
taskReceivers
id taskID receiverID
1 1 4(john)
1 10 2(mike)
1 50 3(brand)
I need result like that:
taskid Receivers
-------------------
1 jone,mike,brand
ONLY FOR PARENT TASKS IT WILL CONCATE RECEIVERS

Answer 1

SQL Server 2005+:
SELECT t.id AS taskid,
STUFF((SELECT ','+ x.name
FROM (SELECT COALESCE(pu.[ArabicName], aut.Name) AS name
FROM CRSTaskReceivers tr
JOIN AD_USER_TBL aut ON aut.id = tr.receiverid
LEFT JOIN PORTAL_USERS pu ON pu.id = aut.id
WHERE tr.crstaskid = t.id
AND tr.receivertype = 1
UNION
SELECT agt.name
FROM CRSTaskReceiver tr
JOIN AD_GROUP_TBL sgt ON agt.id = tr.receiverid
WHERE tr.receivertype = 3
AND tr.crstaskid = t.id) x
FOR XML PATH('')), 1, 1, '')
FROM CRSTasks t
Don't need the function.

Answer 2

Besides the odd string concatenation going on it sure looks like all that could be done in one query instead of four. It's perfectly fine to have more than one criteria in a join. Something along:
FROM CRSTaskReceiver
INNER JOIN CRSTask
ON CRSTaskReceiver.CRSTaskID = CRSTask.ID
INNER JOIN CRS_BuiltinGroup
ON CRSTaskReceiver.ReceiverID = CRS_BuiltinGroup.ID AND CRSTaskReceiver.ReceiverType = 4
WHERE CRSTask.ParentTask = #TaskID
Also the below part of the function seems to do absolutely nothing. What is it meant to do?
DECLARE #tmpLength INT
SET #tmpLength = 0
SET #tmpLength = LEN(#tmp)
IF #tmpLength > 0
BEGIN
SET #tmp = SUBSTRING(#tmp, 0, #tmpLength)
END