Question

I have datetime values stored in a field as strings. They are stored as strings because that’s how they come across the wire and the raw values are used in other places.

For reporting, I want to convert the custom format string (yyyymmddhhmm) to a datetime field in a view. My reports will use the view and work with real datetime values. This will make queries involving date ranges much easier.

How do I perform this conversion? I created the view but can’t find a way to convert the string to a datetime.

Thanks!

Update 1 –

Here’s the SQL I have so far. When I try to execute, I get a conversion error “Conversion failed when converting datetime from character string.”

How do I handle nulls and datetime strings that are missing the time portion (just yyyymmdd)?

SELECT  
        dbo.PV1_B.PV1_F44_C1 AS ArrivalDT,

cast(substring(dbo.PV1_B.PV1_F44_C1, 1, 8)+' '+substring(dbo.PV1_B.PV1_F44_C1, 9, 2)+':'+substring(dbo.PV1_B.PV1_F44_C1, 11, 2) as datetime) AS ArrDT,

        dbo.MSH_A.MSH_F9_C2 AS MessageType,
        dbo.PID_A.PID_F3_C1 AS PRC,
        dbo.PID_A.PID_F5_C1 AS LastName, 
        dbo.PID_A.PID_F5_C2 AS FirstName,
        dbo.PID_A.PID_F5_C3 AS MiddleInitial,
        dbo.PV1_A.PV1_F2_C1 AS Score, 
        dbo.MSH_A.MessageID AS MessageId

FROM    dbo.MSH_A
        INNER JOIN dbo.PID_A ON dbo.MSH_A.MessageID = dbo.PID_A.MessageID
        INNER JOIN dbo.PV1_A ON dbo.MSH_A.MessageID = dbo.PV1_A.MessageID
        INNER JOIN dbo.PV1_B ON dbo.MSH_A.MessageID = dbo.PV1_B.MessageID

Answer 1

declare @S varchar(12)
set @S = '201107062114'

select cast(substring(@S, 1, 8)+' '+substring(@S, 9, 2)+':'+substring(@S, 11, 2) as datetime)

Result:

2011-07-06 21:14:00.000'

This first changes your date string to 20110706 21:14. Date format yyyymmdd as a string is safe to convert to datetime in SQL Server regardless of SET DATEFORMAT setting.

Edit:

declare @T table(S varchar(12))

insert into @T values('201107062114')
insert into @T values('20110706')
insert into @T values(null)

select 
  case len(S)
    when 12 then cast(substring(S, 1, 8)+' '+substring(S, 9, 2)+':'+substring(S, 11, 2) as datetime)
    when 8 then cast(S as datetime)
  end   
from @T

Result:

2011-07-06 21:14:00.000
2011-07-06 00:00:00.000
NULL