Question

How to write such select:

SELECT filename, username, date_time, field1, field2... FROM... JOIN... WHERE...
UNLESS user_downloaded_this_file_today_already

I would like to ignore files downloaded by the same user on the same day. Data example:

12 | file1.jpg | barney | 2012-03-15 12:50:10 | ...
13 | file1.jpg | roger  | 2012-03-15 13:50:10 | ...
14 | file2.jpg | barney | 2012-03-15 14:50:10 | ...
15 | file1.jpg | barney | 2012-03-15 15:50:10 | ...

How do I write a SELECT that would ignore 4th line? Same filename, same user, day difference < 1. Is this actually possible?

Answer 1

Simply use SELECT DISTINCT (assuming you don’t need the numeric column since it’s not in your select):

SELECT DISTINCT  FileName,
                 UserName,
                 Date_Time
FROM             [YourTable]

If your Date_Time column contains times and not just 00:00:00, you’ll need to strip out the time for DISTINCT to work properly:

SELECT DISTINCT  FileName,
                 UserName,
                 CONVERT(DATETIME, FLOOR(CONVERT(FLOAT, Date_Time))) AS Date_Time
FROM             [YourTable]

Here’s an example of the date stripping in action.