SQL选择问题：每天获取最大值

Question

I have a problem with my SQL select, I need to get the max value for the column ( currentcount ) per each day for the period between DateDebut and DateFin , but the returned result show me multiple values.

My SQL statement:

DECLARE @dateDebut DATE, 
        @dateFin DATE, 
        @SITA_METIER VARCHAR(20), 
        @DEFSITE VARCHAR(20);

SET @dateDebut = '01/01/2017';
SET @dateFin = '31/12/2018';


SELECT DISTINCT
    CONVERT(DATE, attemptdate) AS Date, 
    MAX(currentcount) AS MAXUSERS
FROM
    logintracking 
WHERE
    attemptdate BETWEEN CONVERT(DATE, @dateDebut) AND CONVERT(DATE, @dateFin)
    AND logintracking.clientaddr IN ('10.118.254.21', '10.118.254.156') 
GROUP BY
    attemptdate, currentcount

Result:

enter image description here

Desired result: only the max value for the column ( currentcount ) for each day

PS: attemptdate type is Timestamp , that's why I need to cast it into a simple date.

I also tried to use 'having' function but still get multiple values

Answer 1

You already use GROUP BY the distinct is no make sense, so the distinct can be removed.

then you just modify CONVERT(Date,attemptdate) instead of attemptdate in Group by , and only need to group by CONVERT(Date,attemptdate)

select CONVERT(Date,attemptdate) as Date, max(currentcount) as MAXUSERS
from logintracking 
where attemptdate between @dateDebut and @dateFin
  and logintracking.clientaddr in ('10.118.254.21', '10.118.254.156') 
group by CONVERT(Date,attemptdate)

Note:

Your @dateDebut and @dateFin already are Date type. No need to use CONVERT function.