Query Based on Current Status of a Sub Item - sql

Question

Trying to write a query to display the current status of services in a company department. What I have written is just not working. I feel like I am going in the wrong direction.
SELECT MAX(v_StatusEvents.EventTimeStamp) as EventTimeStamp
, MAX(v_StatusEvents.StatusTypeID) as StatusTypeID
, v_StatusEvents.ServiceID
, v_StatusEvents.StatusTypeDescription
, v_StatusEvents.ServiceName
, v_StatusEvents.CategoryName
FROM v_StatusEvents
WHERE v_StatusEvents.CategoryID = 100
AND YEAR(v_StatusEvents.EventTimeStamp) = YEAR(getdate())
AND MONTH(v_StatusEvents.EventTimeStamp) = MONTH(getdate())
AND DAY(v_StatusEvents.EventTimeStamp) = DAY(getdate())
GROUP BY v_StatusEvents.ServiceID
, v_StatusEvents.StatusTypeDescription
, v_StatusEvents.ServiceName
, v_StatusEvents.CategoryName
I have three CATEGORIES: (100 - Internet, 101 - Applications, and 102 - Network).
Each CATEGORY contains SERVICES.
As an example, I have three SERVICES that belong to the CATEGORY Interenet: (50 - Internal, 51 - External, 52 - Development).
Each SERVICE will always have at least one status record for the current date.
The CURRENT STATUS will be set to one of three different STATUS TYPES values: 1 = no issue, 2 = disruption, 3 = critical.
I want to show the highest STATUS TYPE for each category for today.
Here is a sample record set for today's date.
SeID CatID EventTimeStamp SvcID StatTypeID
201 100 11/11/2012 12:01am 52 1
202 100 11/11/2012 12:01am 51 1
203 100 11/11/2012 12:01am 50 1
204 100 11/11/2012 08:00am 51 3
205 100 11/11/2012 10:50am 50 2
206 100 11/11/2012 11:00am 50 1
207 100 11/11/2012 11:25am 52 2
As you can see, there was a disruption problem with the Internal web site at 10:50m, but it was resolved at 11:00am.
There is an ongoing critical issue with the External web site that has not yet been resolved. I would like the for the query to return the value 3 because this is the highest CURRENT STATUS for a SERVICE that has not been resolved.
(If all services had "no issue", I would expect the query to return the value 1)
Thanks,
crjunk

Answer 1

This is where I find CTEs (Common Table Expressions) useful. They allow you to break the problem apart into steps that you can easily solve. Let's apply that here.
First, get the max status for each service/day:
SELECT CatID, SvcID, MAX(StatTypeID) As MaxStatus
FROM v_StatusEvents
WHERE EventTimeStamp >= cast(cast(current_timestamp as Date) as datetime)
GROUP BY CatID, SvcID
Now that we have this information, we can find that most recent time today that each of these events occured:
WITH StatusInfo As
(
SELECT CatID, SvcID, MAX(StatTypeID) As MaxStatus
FROM v_StatusEvents
WHERE EventTimeStamp >= cast(cast(current_timestamp as Date) as datetime)
GROUP BY CatID, SvcID
)
SELECT se.CatID, se.SvcID, se.StatTypeID, MAX(EventTimeStamp) As EventTimeStamp
FROM v_StatusEvents se
INNER JOIN StatusInfo si ON se.CatID = si.CatID AND se.SvcID = si.SvcID AND se.StatTypeID = si.MaxStatus
WHERE EventTimeStamp >= cast(cast(current_timestamp as Date) as datetime)
You might choose instead to use the sequence ID to narrow it down here, in case you could have two events with the same timestamp for a service. Now that we have this information, we can go back to the table one more time to pick up any other fields we might want (in this case, sequence ID):
WITH StatusInfo As
(
SELECT CatID, SvcID, MAX(StatTypeID) As MaxStatus
FROM v_StatusEvents
WHERE EventTimeStamp >= cast(cast(current_timestamp as Date) as datetime)
GROUP BY CatID, SvcID
), StatusAndTimeInfo As
(
SELECT se.CatID, se.SvcID, se.StatTypeID, MAX(EventTimeStamp) As EventTimeStamp
FROM v_StatusEvents se
INNER JOIN StatusInfo si ON se.CatID = si.CatID AND se.SvcID = si.SvcID AND se.StatTypeID = si.MaxStatus
WHERE EventTimeStamp >= cast(cast(current_timestamp as Date) as datetime)
)
SELECT se.*
FROM v_StatusEvents se
INNER JOIN StatusAndTimeInfo sati ON se.CatID = sati.CatID AND se.SvcID = sati.SvcID AND se.StatTypeID = sati.StatTypeID AND se.EventTimeStamp = sati.EventTimeStamp
WHERE EventTimeStamp >= cast(cast(current_timestamp as Date) as datetime)
Note again that you might prefer to use the SeID (which I presume is a sequence ID) on this last iteration rather than timestamp. Note also that this is NOT the only way to solve this problem, or even likely the fastest. In fact, it would be possible to re-write this using only subqueries or joins. But this is any easy method you can use to get something that works, and can be easily understood later.

Answer 2

Ended up coming with the following solution:
SELECT (IsNull(MAX(tblStatusTypes.StatusTypeImgURL), (SELECT tblStatusTypes.StatusTypeImgURL FROM tblStatusTypes WHERE tblStatusTypes.StatusTypeID = 1)))
FROM tblStatusTypes
WHERE tblStatusTypes.StatusTypeID in (
SELECT MAX(StatusTypeID)
FROM
( SELECT vse.StatusTypeID, vse.ServiceID, vse.EventTimeStamp
FROM v_StatusEvents vse,
(SELECT MAX(EventTimeStamp)AS MaxDate
,ServiceID
FROM v_StatusEvents
WHERE EventTimeStamp >= Cast(Cast(CURRENT_TIMESTAMP AS DATE) AS DATETIME)
AND CategoryID = #CategoryID
GROUP BY ServiceID) MaxResults
WHERE vse.ServiceID = MaxResults.ServiceID
AND vse.EventTimeStamp = MaxResults.MaxDate
) MaxStatusType )