Microsoft SQL MAX() Not Including Rows with NULLs - sql

Question

I work in a law firm with a case management system which links an interface to a SQL db. I am writing queries in SSRS to run reports. I am trying to run a report on case information. Some of the information is right in the "cases" table (or vcases view), but I'm also trying to link information from a "demands_offers" table. Each case can have multiple demands and offers, so I am using a MAX function in a join to extract only the most recent demand record per case. Unfortunately, doing this eliminates cases which have no demands. I need all the cases to show up.
I have tried using a CASE statement nested in the MAX function to convert NULLS or empty fields to a random early date, but I still can't get all of the cases to appear in the report.
Any ideas? I am a relative newbie with SQL and have no formal training. Any help would be greatly appreciated. You can see the code below. (P.S. I don't think that I have the rights to create a temporary table.)
SELECT vc.case_number AS "Matter ID", vc.style, vc.atty2_name AS "Handling Attorney", m.max_demands_date, do.demands, do.demands_notes, sa.authorized,
(SELECT TOP 1 vl.computename
FROM vcases vca
LEFT OUTER JOIN case_parties cp
ON vca.case_sk = cp.case_sk
JOIN case_parties cpp
ON cp.parent_sk = cpp.case_parties_sk
JOIN vlegal_entity vl
ON vl.legal_entity_sk = cp.entity_sk
JOIN vlegal_entity vlp
ON vlp.legal_entity_sk = cpp.entity_sk
WHERE (vca.case_sk = vc.case_sk) AND (cpp.role_sk = '3557') AND (cp.role_sk = '3986') ) AS "Plaintiff//'s Attorney",
(SELECT cp.reference_number
FROM cases AS ca
LEFT OUTER JOIN case_parties AS cp
ON ca.case_sk = cp.case_sk
WHERE (cp.role_sk = '3706')
AND (ca.case_sk = vc.case_sk)) AS "Claim Number"
FROM
vcases vc
LEFT OUTER JOIN
case_parties cp ON vc.case_sk = cp.case_sk
LEFT OUTER JOIN
vlegal_entity vl ON cp.entity_sk = vl.legal_entity_sk
LEFT OUTER JOIN
settle_authority sa ON vc.case_sk = sa.case_sk
LEFT OUTER JOIN
demands_offers do ON vc.case_sk = do.case_sk
INNER JOIN
(SELECT DISTINCT max(
(CASE WHEN do.demands_date = '' THEN '1/1/1900 00:00:00'
ELSE do.demands_date
END)
) as "max_demands_date", vc.case_sk
FROM vcases AS vc
JOIN demands_offers AS do ON vc.case_sk = do.case_sk
GROUP BY vc.case_sk) AS m
ON vc.case_sk = m.case_sk AND
do.demands_date = m.max_demands_date
WHERE (vc.closed_ind = 'O') AND (cp.role_sk = '3816') AND (vl.client_number = 'EAS-01') AND (vc.lawtype_code <> 'FA')
ORDER BY vc.case_number

Answer 1

Your query can probably be written to be much more compact and better performing, but to start you off, this is the part that is removing the rows without demands:
INNER JOIN
(SELECT DISTINCT max(
(CASE WHEN do.demands_date = '' THEN '1/1/1900 00:00:00'
ELSE do.demands_date
END)
) as "max_demands_date", vc.case_sk
FROM vcases AS vc
JOIN demands_offers AS do ON vc.case_sk = do.case_sk
GROUP BY vc.case_sk) AS m
ON vc.case_sk = m.case_sk AND
do.demands_date = m.max_demands_date
It needs to be
LEFT JOIN
(SELECT DISTINCT max(
(CASE WHEN do.demands_date = '' THEN '1/1/1900 00:00:00'
ELSE do.demands_date
END)
) as "max_demands_date", vc.case_sk
FROM vcases AS vc
JOIN demands_offers AS do ON vc.case_sk = do.case_sk
GROUP BY vc.case_sk) AS m
ON vc.case_sk = m.case_sk AND
do.demands_date = m.max_demands_date
The reason is that an (A INNER JOIN B) keeps records only when it is possible to match rows in A to rows in B. When there is no demand, the derived table (subquery) returns NULL for max_demands_date, which cannot be matched by do.demands_date = m.max_demands_date. This causes the case record to get removed.