How to use multiple conditional statements using SQL in Visual Studio SSRS 2008

Question

I am trying to pull calculated data out of a SQL database using Visual Studio SSRS 2008. I am having problems trying to use conditionals in my select/from/where statements. One example of what I'm trying to do is to find the total number of failures in a 24 hour period(from 10:00am yesterday to 10:00am today) from samples taken every 15 minutes. I'm reporting on a gas plant that has gas running through valves when they are open. Gas that goes trough a particular open valve gets ignited in a combustion chamber. When this happens, a failure occurs if the valve is open and the temperature in the combustion chamber is less than 1400 degrees. I currently have a query that gives me data for the valve status and the combustion chamber temp every 15 minutes. As I said, I only care about when the valve has a status of 2, which is open, and the combustion chamber temp is < 1400 at the same time. I have copied my current query below as well as a sample of the resulting data. As you can see, the current query does not include my necessary conditionals. I need to add code that looks something like this:

COUNT (IF RTO_FCV601_SSTS=2 AND RTO_COMB1TEMP < 1400)

---

SET NOCOUNT ON
DECLARE @StartDate DateTime
DECLARE @EndDate DateTime
SET @StartDate = DateAdd(HOUR,-24,GetDate())
SET @EndDate = GetDate()
SET NOCOUNT OFF
SELECT temp.TagName ,DateTime,Value
From (
SELECT  * 
 FROM History
 WHERE History.TagName IN ('RTO_FCV601_STS','RTO_COMB1TEMP')
 AND wwRetrievalMode = 'Cyclic'
 AND wwCycleCount = 96
 AND wwVersion = 'Latest'
 AND DateTime >= @StartDate
 AND DateTime <= @EndDate) temp
 WHERE temp.StartDateTime >= @StartDate

---

Resulting data:
TagName         DateTime                    Value
RTO_FCV601_STS  2013-04-08 15:44:40.6600000 2
RTO_COMB1TEMP   2013-04-08 15:44:40.6600000 1663
RTO_FCV601_STS  2013-04-08 15:59:50.1340000 2
RTO_COMB1TEMP   2013-04-08 15:59:50.1340000 1604
RTO_FCV601_STS  2013-04-08 16:14:59.6080000 2
RTO_COMB1TEMP   2013-04-08 16:14:59.6080000 1557
RTO_FCV601_STS  2013-04-08 16:30:09.0810000 0
RTO_COMB1TEMP   2013-04-08 16:30:09.0810000 1704
RTO_FCV601_STS  2013-04-08 16:45:18.5550000 2
RTO_COMB1TEMP   2013-04-08 16:45:18.5550000 1576
RTO_FCV601_STS  2013-04-08 17:00:28.0290000 2
RTO_COMB1TEMP   2013-04-08 17:00:28.0290000 1645

If I can't solve this problem within SQL, I'm hoping I can find a way within the Visual Studio SSRS. Thanks in advance for the help!

Answer 1

in my idea and by having no look on your tables....I say If your DateTime is uniq just for those two states try this query although I advise you (and in my idea) it's a little illogical to have join on Datetime below...you can optimize it yourself...but you can use "case when" statement anyway

SET NOCOUNT ON
DECLARE @StartDate DateTime
DECLARE @EndDate DateTime
SET @StartDate = DateAdd(HOUR,-24,GetDate())
SET @EndDate = GetDate()
SET NOCOUNT OFF
SELECT Sum(case when temp.Value = 2 and temp2.value< 1400 then 1 else 0 end ) 
AS 'failureCount'
From (
 SELECT  *
 FROM History
 WHERE History.TagName IN ('RTO_FCV601_STS')
 AND wwRetrievalMode = 'Cyclic'
 AND wwCycleCount = 96
 AND wwVersion = 'Latest'
 AND DateTime >= @StartDate
AND DateTime <= @EndDate)as temp 
join
 (SELECT  * FROM History
   WHERE History.TagName IN ('RTO_COMB1TEMP')
   AND wwRetrievalMode = 'Cyclic'
   AND wwCycleCount = 96
   AND wwVersion = 'Latest'
   AND DateTime >= @StartDate
   AND DateTime <= @EndDate)as temp2 on temp.DateTime = temp2.DateTime

WHERE temp.StartDateTime >= @StartDate and temp2.StartDateTime >= @StartDate