Concatenating Int columns

I have a table called Field_Data and the data in the table looks like:

Date                          Track_ID          Item#
2011-02-25 00:00:00.000       70212             1
2011-02-25 00:00:00.000       7021开发者_StackOverflow2             2
2011-03-09 00:00:00.000       70852             1
2011-03-09 00:00:00.000       70852             3

I am trying to get output as:

Date                          Final_ID
2011-02-25 00:00:00.000       70212_1
2011-02-25 00:00:00.000       70212_2
2011-03-09 00:00:00.000       70852_1
2011-03-09 00:00:00.000       70852_3

I tried doing something like this:

Select Date,Track_ID + '_' + Item# AS Final_ID
From Field_Data

But it gave me following error:

Msg 245, Level 16, State 1, Line 1

Conversion failed when converting the varchar value '_' to data type int.

Can anyone help me on how to do this?

You need to cast the INT fields as varchar:

Select Date,CAST(Trakc_ID as varchar(20)) + '_' + CAST(Item# as varchar(20)) as Final_ID
From Field_Data

Heads up for any new page visitors, in SQL Server 12+, there's a CONCAT function available.

SELECT CONCAT([Date], [TrackId], '_', [ItemNumber]) AS FinalId
FROM FieldData