Sql query with sql subquery - sql

Question

Hi all I have written the following query to combine the results from 3 tables(tblQuestions,tblReplies,tblTechnology and display the required results as follows
SELECT tech.DatePosted,
tech.QuestionID,
tech.TechnologyName,
tblr3.TechID,
tblr3.QuestionTitle,
tblr3.UserName,
tblr3.ReplyCount,
tblr3.viewCount,
tblr3.date,
tblr3.RepliedName
FROM (SELECT tblr1.DatePosted,
tblr1.QuestionID,
tblr2.TechID,
tblr2.QuestionTitle,
tblr2.UserName,
tblr2.ReplyCount,
tblr2.viewCount,
tblr1.date,
tblr1.RepliedName
FROM (SELECT tblq.DatePosted,
tblq.TechID,
tblq.QuestionID,
tblq.RepliedName,
tblq.QuestionTitle,
tblq.UserName,
tblq.ReplyCount,
tblq.viewCount,
tblq.date
FROM (SELECT q.DatePosted,
q.TechID,
q.QuestionID,
q.QuestionTitle,
q.UserName,
q.ReplyCount,
q.viewCount,
r.date,
r.UserName AS RepliedName
FROM tblQuestions AS q, tblReplies AS r
WHERE r.QuestionID = q.QuestionID
AND r.TechID = q.TechID
AND q.TechID = 1) AS tblq,
(SELECT r.QuestionID,
max(r.date) AS PostedDate
FROM tblReplies AS r
GROUP BY QuestionID) AS tblr
WHERE tblq.QuestionID = tblr.QuestionID
AND tblq.date = tblr.PostedDate) AS tblr1
RIGHT OUTER JOIN
(SELECT q.QuestionID,
q.TechID,
q.UserName,
q.viewCount,
q.ReplyCount,
q.QuestionTitle
FROM tblQuestions AS q
WHERE q.TechID = 1) AS tblr2
ON tblr2.QuestionID = tblr1.QuestionID) AS tblr3
LEFT OUTER JOIN
(SELECT q.QuestionID,
q.DatePosted,
t.TechID,
t.TechName AS TechnologyName
FROM tblTechnology AS t, tblQuestions AS q
WHERE q.TechID = t.TechID) AS tech
ON tblr3.TechID = tech.TechID
AND tblr3.QuestionID = tech.QuestionID
AND tech.TechID = 1
Which gives me the following result as expected but getting NULL at some fields where data to be present
In place of NULL i need to pull out some data which is present in tblQuestions, also is it possible to reduce the query.
From OPs Comment:
I am trying to pull out the questiontitle,username,questionid from tblquestions along with replycount and viewcount and the latest replys that are posted for that questions based on QuestionID and Technology ID from tblreplys

Answer 1

Your query is basically this:
SELECT
blah
FROM
(
(SELECT
blah
FROM
Questions
INNER JOIN Replies ON QuestionID AND TechID) tblr1
RIGHT JOIN Questions tblr2 ON QuestionID
) tblr3
LEFT JOIN Technologies ON tblr3.tblr1.QuestionID = Technologies.QuestionID
I know that isn't a valid query but bear with me. tblr1contains an INNER JOIN between questions and answers. However because there are no answers to the salary question these records are NULLfor the salaryquestion. The RIGHT JOIN to Questions then introduces the salary question and that exists in the tblr3 result set because it is a RIGHT JOIN even though tblr1 is null for this question.
The LEFT JOIN then to technologies is based on the QuestionID within tblr3 which is really the QuestionID from tblr1. From looking at the column list for the tblr3 sub query, if you change tblr1.QuestionID to tblr2.QuestionID this will ensure that unanswered questions join on to the Technology table
EDIT: I think the following query will give you your results and is much simpler:
WITH LatestReplies AS
(
SELECT
ReplyID,
QuestionID,
ReplyDate,
UserName,
Reply
FROM
(SELECT
ReplyID,
QuestionID,
ReplyDate,
UserName,
Reply,
ROW_NUMBER() OVER (PARTITION BY QuestionID ORDER BY ReplyDate DESC) ReplyOrder
FROM
tblReplies) A
WHERE
ReplyOrder = 1
)
SELECT
tblQuestions.DatePosted,
tblQuestions.QuestionID,
tblTechnology.TechnologyName,
tblQuestions.TechID,
tblQuestions.QuestionTitle,
tblQuestions.UserName,
tblQuestions.ReplyCount,
tblQuestions.ViewCount,
LatestReplies.ReplyDate,
LatestReplies.UserName RepliedName
FROM
tblQuestions
LEFT JOIN tblTechnology ON tblQuestions.TechID = tblTechnology.TechID
LEFT JOIN LatestReplies ON tblQuestions.QuestionID = LatestReplies.QuestionID

Answer 2

Solved with the following after all
select
FI.QuestionID,
FI.QuestionTitle,
FI.UserName,
FI.DatePosted,
FI.[date],
FI.RepliedName,
FI.viewCount,
FI.ReplyCount,
FI.ReplyMsg,
TT.TechID,
TT.TechName
from
tblTechnology TT,
(select distinct
TQ.TechID,
TQ.QuestionID,
TQ.QuestionTitle,
TQ.UserName,
TQ.DatePosted,
TR.[date],
TR.UserName as RepliedName,
TQ.viewCount,
TQ.ReplyCount,
TR.ReplyMsg
from
tblQuestions TQ
LEFT OUTER JOIN tblReplies TR ON
TR.TechID=TQ.TechID
and TR.QuestionID = TQ.QUESTIONID
and TR.[date] in (select
MAX(TR.[date])
from
tblReplies TR
group by
TR.QuestionID)
) FI
where
FI.TechID=TT.TechID
and TT.TechID=#TechID