troubleshooting Question

SQL Server - Simple Group by question.

Avatar of Bill Park
Bill ParkFlag for United States of America asked on
SQLMicrosoft SQL Server
6 Comments1 Solution12 ViewsLast Modified:
I need to build a stored procedure that produces a snapshot of the last status of a Device in telemetry:

CREATE TABLE [dbo].[vrtEvents](
   [Device] [int] NULL,
   [Loc] [tinyint] NULL,
   [CaptureTime] [time](0) NULL,
   [Here] [bit] NULL

I need to show the most recent (per CaptureTime) for each Device showing the Loc and In values but when I try to do this:

SELECT Device, MAX(Loc) AS Loc, MAX(CaptureTime) AS CaptureTime, MAX(Here) AS In
FROM   dbo.vrtEventSim
HAVING (Device = Device)

I get "Operand data type bit is invalid for max operator."

So I try this:

SELECT Device, MAX(CaptureTime) AS CaptureTime, MAX(Loc) AS Loc, MAX(CAST(Here AS Int)) AS Here
FROM   dbo.vrtEventSim
HAVING (Device = 808)
which returns:
Device   CaptureTime   Loc   Here
808   20:38:21   55   1


FROM dbo.vrtEventSim
WHERE Device = 808
ORDER BY CaptureTime Desc
which returns:
Device   Loc   CaptureTime   Here
808   5   20:38:21   0

So the Group query returns a different Here value than the vanilla query.

What am I missing?

Thank you.
Brian Crowe
Database Manager
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