select count absences of employees on each day

Question

alright, so lets say i have three tables, as follows :
employees( ID , name)
sessions( ID , starts_at, ends_at, day)
absences( ID , employeeID, sessionID)

lets say there are multiple sessions per day.
is it possible to select count the Absences of employees from sessions for each distinct day on the sessions table and group them as follows :

--------------------------------
| Name |2011-01-15| 2011-01-16 | 
|      |          |            |
|john  |  2       |   0        |
|dave  |  4       |    1       |

(number of columns (days) depends on number of days on the sessions table, lets say i only want those of last or current week
thank you.

Answer 1

You should use the PIVOT statement. There it goes:

SELECT Name, [2011-01-15], [2011-01-16]
FROM    
(SELECT  [Day],Name
    FROM [Absences] A left join
         [Sessions] S on A.sessionID = S.ID
    GROUP BY [Day],Name) AS SourceTable
PIVOT
(
COUNT([Day])
FOR [Day] IN ([2011-01-15], [2011-01-16])
) AS PivotTable;

Answer 2

Look up pivot table . On some RDBMS, this is built in.

Answer 3

I'm thinking you are talking MySQL and you want to do a pivot table. Go to ArtfulSoftware's MySQL site and review the pivot table tutorials: http://www.artfulsoftware.com/infotree/queries.php