DATEDIFF rounding to the nearest 30 minutes

Question

I am using datediff to get the difference between two datetimes:

DATEDIFF(hh, CAST(CAST(dbo.QuickLabDump.[Date Entered] AS DATE) AS DATETIME) 
    + CAST(dbo.QuickLabDump.[Time Entered] AS TIME), 
   CAST(CAST(dbo.QuickLabDump.[Date Completed] AS DATE) AS DATETIME) 
    + CAST(dbo.QuickLabDump.[Time Completed] AS TIME)) AS [Hours TurnAround]

I don't understand the behavior that I am getting from this statement but what I need is anything that is >= :30, round up, if not, round down,

question how do I get it to round down when less than 30 minutes and round the hours up if greater or equal to 30 minutes?

Answer 1

You should calculate the DATEDIFF in minutes and do a ROUND then:

ROUND(CAST(DATEDIFF(MINUTES, CAST(CAST(dbo.QuickLabDump.[Date Entered] AS DATE) AS DATETIME) 
                      + CAST(dbo.QuickLabDump.[Time Entered] AS TIME), CAST(CAST(dbo.QuickLabDump.[Date Completed] AS DATE) AS DATETIME) 
                      + CAST(dbo.QuickLabDump.[Time Completed] AS TIME)) AS FLOAT)/60,0)  AS [Hours TurnAround]