Grouping the results of an SQL Select

Question

I'm trying to achieve what I thought was a simple grouping of results from an mssql select statement as shown below;

SELECT
    DATEPART( day, Review.[LocalTimeGenerated] ) AS DayNum,
    Review.[LocalTimeGenerated] AS LocalDate,
    ( Users.[FirstName] + ' ' + Users.[SecondName] ) AS FullName,
    SUBSTRING(
        Review.[Text],
        PATINDEX(
            '%into %',
            Review.[Text]
        ) + 5,
    50
) AS LastDoorEntered                                        /* return only the door name */

FROM [LOGS].[dbo].[Review] Review

INNER JOIN [DATA].[dbo].[TUser] Users
ON Review.[Entity_2_ID] = Users.[ID]

WHERE Review.[LocalTimeGenerated] > GETDATE() - 9           /* get the last 9 days */ 
AND Review.[Entity_3_ID] = '4503603922337793'               /* id of the door? */
AND ( Users.[FirstName] + ' ' + Users.[SecondName] ) = '[username]'

ORDER BY [Fullname] ASC, [LocalDate] DESC

With the following results;

DayNum  LocalDate                       FullName     LastDoorEntered
8       2018-03-08 07:20:08.7370000     [username]   Main Office Entrance
7       2018-03-07 08:15:31.5970000     [username]   Main Office Entrance
6       2018-03-06 14:41:43.3230000     [username]   Main Office Entrance
6       2018-03-06 08:52:15.9870000     [username]   Main Office Entrance
5       2018-03-05 08:52:45.4170000     [username]   Main Office Entrance
1       2018-03-01 14:43:12.7670000     [username]   Main Office Entrance
1       2018-03-01 13:10:29.6400000     [username]   Main Office Entrance
1       2018-03-01 12:18:57.1670000     [username]   Main Office Entrance
1       2018-03-01 11:32:17.5970000     [username]   Main Office Entrance
1       2018-03-01 10:43:04.2170000     [username]   Main Office Entrance
1       2018-03-01 08:05:00.1530000     [username]   Main Office Entrance
28      2018-02-28 15:19:22.4270000     [username]   Main Office Entrance
28      2018-02-28 13:17:04.9100000     [username]   Main Office Entrance
28      2018-02-28 12:06:50.3970000     [username]   Main Office Entrance
28      2018-02-28 08:52:09.6600000     [username]   Main Office Entrance

The trouble I'm having is that I need to return a grouped result based on the day (essentially I need to see only the first entry per day). Below is what the result needs to be;

DayNum  LocalDate                       FullName     LastDoorEntered
8       2018-03-08 07:20:08.7370000     [username]   Main Office Entrance
7       2018-03-07 08:15:31.5970000     [username]   Main Office Entrance
6       2018-03-06 08:52:15.9870000     [username]   Main Office Entrance
5       2018-03-05 08:52:45.4170000     [username]   Main Office Entrance
1       2018-03-01 08:05:00.1530000     [username]   Main Office Entrance
28      2018-02-28 08:52:09.6600000     [username]   Main Office Entrance

I was hoping that I could simply use GROUP BY DayNum, but apparently you can't group by an alias.

Invalid column name 'DayNum'.

Moving the logic down to the GROUP BY clause didn't work either (...not contained in either an aggregate function or the GROUP BY clause).

I tried doing two separate SELECT's and merging them back together by an ID column (unused in the example above), with no success. No luck with using the max trick shown on Select multiple columns from table but Group By one either.

Is there a way I can get this to work, or am I stuck doing it after the fact in the front end?

Answer 1

You can't group by an alias, but in most SQL implementations you can group by the output of a function. Simply group by DATEPART( day, Review.[LocalTimeGenerated] ) and it should work.

You'll of course need to wrap all your other selections in aggregation functions (eg min(Review.[LocalTimeGenerated]) AS LocalDate )

Answer 2

You can use ROW_NUMBER

SELECT * FROM (
    SELECT
        DATEPART( day, Review.[LocalTimeGenerated] ) AS DayNum,
        Review.[LocalTimeGenerated] AS LocalDate,
        ( Users.[FirstName] + ' ' + Users.[SecondName] ) AS FullName,
        SUBSTRING(
            Review.[Text],
            PATINDEX(
                '%into %',
                Review.[Text]
            ) + 5,
        50
    ) AS LastDoorEntered                                        /* return only the door name */
    , ROW_NUMBER() OVER(PARTITION BY CAST(Review.[LocalTimeGenerated] AS DATE) ORDER BY Review.[LocalTimeGenerated]) RN 

    FROM [LOGS].[dbo].[Review] Review

    INNER JOIN [DATA].[dbo].[TUser] Users
    ON Review.[Entity_2_ID] = Users.[ID]

    WHERE Review.[LocalTimeGenerated] > GETDATE() - 9           /* get the last 9 days */ 
    AND Review.[Entity_3_ID] = '4503603922337793'               /* id of the door? */
    AND ( Users.[FirstName] + ' ' + Users.[SecondName] ) = '[username]'
) T
WHERE RN = 1
ORDER BY [Fullname] ASC, [LocalDate] DESC