Question

I want to compare and count rows in the same datatabe.

myDataTable

hours_id(PK) | _person_id | _project_id | date_of_hour
 1       |    pe1     |    pr1      | 13.10.2011
 2       |    pe22    |    pr1      | 13.10.2011
 3       |    pe1     |    pr1      | 15.10.2011 *
 4       |    pe1     |    pr1      | 13.10.2011
 5       |    pe1     |    pr1      | 13.10.2011
 6       |    pe22    |    pr22     | 13.10.2011
 7       |    pe1     |    pr22     | 15.10.2011 *
 8       |    pe1     |    pr1      | 15.10.2011 *
 9       |    pe22    |    pr22     | 13.10.2011
 10      |    pe22    |    pr22     | 13.10.2011
 11      |    pe1     |    pr1      | 16.10.2011 **

_project_id(GUID)

In my program I can choose _person_id_2 = pe1, date_of_begin = 13.10.2011 and date_of_end = 15.10.2011. I want to get this result:

 pe1    pr1   13.10.2011  3   //(count 3 rows are the same)(ROWS 1,4,5)
 pe1    pr1   15.10.2011  2   //(ROWS 3,8)
 pe1    pr22  15.10.2011  1   //(ROW 7)

And when I choose _person_id_2 = pe22, date_of_begin = 13.10.2011 and date_of_end = 15.10.2011 I want to get this result:

 pe22   pr1   13.10.2011  1   //(ROW 2)
 pe22   pr22  13.10.2011  1   //(ROW 6)
 pe22   pr22  15.10.2011  2   //(ROWS 9,10)

I’m using SQL Server 2008. Hope you understand what I’m trying to ask.

Answer 1

Do you need a group by clause + count aggregation function:

Select 
   _person_id, _project_id, date_of_hour, count(*)
from
   myDataTable
where 
   _person_id = 'pe1'
 and
   date_of_hour between '13.10.2011' and '15.10.2011'
group by 
 _person_id, _project_id, date_of_hour

Notice: I understand that when you write ‘13.10.2011’ you are talking about a well formed date and date_of_hour is in date or datetime format. If is not the case, you should cast your strings and columns to a valid date.