SQL Max（）返回多个值

Question

Good morning/afternoon & thank you for checking on this, I'm struggling to figure out what I'm missing.

Attempting to put together a schedule system off the results (separate task) but because our schedules change several times a day/week its creating too many duplicates.

Select modified, local_Start_Time, local_End_Time, seg_code, Date, employee

from schedule_table

Where employee= '###' and seg_code = ‘schedule’
and Date in ('20160606', '20160607', '20160608', '20160609') 

group by modified
,local_start_time
,local_end_time
,seg_code
,date
,employee

When I run this, I get this Table as expected.

I tried adding max () around the 'modified' select to limit it to the latest entry, but that did not change anything from the above. I then added

 max(Local_START_Time)
,max(Local_END_time)
,max(modified)

to the selects, which did limit it to 1 line per employee however its now taking the opposite entries from what it should per this [table 2][2]

I tried adjusting it from max to min on the start/end times and it fixed some and broke others.

I'm fairly new to SQL and have tried looking at other questions/videos but to no avail. I understand the logic where it's taking the 'max' modified as the most recent time entry, and then max (highest starting / end time) from those 2 cells but in a perfect world I'd prefer only one max value (modified) and then it pairs that to the start & end times.

Can anyone guide me in the right direction with what I'm missing to make this work either with 1 max statement, or if using all 3 / a different one entirely?

Using SQL Management Studio & apologies if I'm missing any other key details, thank you for your help and looking forward to learning more & helping others!

Edit To clarify the challenge I'm having, Updated Image , cells in green are both the latest updated schedule per date whereas the cells in red are what is being captured by the max(start/end time).

Hope that helps

Answer 1

If you want the max of the value you should perform the query without the group by you have setted for the column in aggregation function (max)

Select max(modified), max(local_Start_Time), max(local_End_Time), seg_code, Date, employee

from schedule_table

Where employee= '###' and seg_code = ‘schedule’
and Date in ('20160606', '20160607', '20160608', '20160609') 

group by seg_code
,date
,employee 

for getting the row related to max(modified) you should instead use a subquery

    Select modified, local_Start_Time, local_End_Time, seg_code, Date, employee
    from schedule_table
    where modified = (  select max(modified)
                         from schedule_table
                         Where employee= '###' and seg_code = ‘schedule’
                        and Date in ('20160606', '20160607', '20160608', '20160609') 
    );

And for get only the employee then

    Select modified, local_Start_Time, local_End_Time, seg_code, Date, employee
    from schedule_table
    where modified = (  select max(modified)
                         from schedule_table
                         Where employee= '###' and seg_code = ‘schedule’
                        and Date in ('20160606', '20160607', '20160608', '20160609') 
    )
    and employee= '###'
    ;

Answer 2

When you add the max() , you also need to remove the fields from the group by :

Select max(modified), max(local_Start_Time), max(local_End_Time),
       seg_code, Date, employee
from schedule_table
where employee= '###' and seg_code = 'schedule' and
      Date in ('20160606', '20160607', '20160608', '20160609') 
group by seg_code, date, employee;

Otherwise, the query returns a separate row for each value of the column -- and the max() will simply be the value in the row.

Answer 3

So here's what I got:

SELECT DISTINCT 
    [date], 
    employee, 
    max(modified) OVER (PARTITION BY [date]) AS max_modified,
    max(start_time) OVER (PARTITION BY [date]) AS max_start, 
    max(end_time) OVER (PARTITION BY [date]) AS max_end
FROM Table_1
GROUP BY 
    [date], employee, modified, start_time, end_time

OR if you wanted to separate out by date and modified date,

SELECT DISTINCT 
    [date], 
    employee, 
    max(modified) OVER (PARTITION BY [date],employee) AS max_modified, 
    max(start_time) OVER (PARTITION BY [date]) AS max_start, 
    max(end_time) OVER (PARTITION BY [date]) AS max_end
FROM Table_1
GROUP BY [date], employee, modified, start_time, end_time