如何通过分组或计数功能使用内部联接

Question

I'm use this SQL query to fetch data from a access database

SELECT  Absence.date_, stages.name, course.course_name, student.name AS st_name 
FROM  (((Absence INNER JOIN  course ON Absence.course_id = course.ID) 
INNER JOIN       stages ON course.id_stage = stages.ID) 
INNER JOIN     student ON Absence.student_id = student.ID AND stages.ID = student.stage_id`

when i wont to group the field or get count of field it show to me this error message

Tried to execute a query that does not include the specified expression 'Absence.date_' as part of an aggregate function

how can i get number of row ,distinct it by st_name , and group by stage name or course name

Answer 1

For getting the count you should use

SELECT  Absence.date_, stages.name, course.course_name, student.name AS st_name, count(*) 
FROM  (((Absence INNER JOIN  course ON Absence.course_id = course.ID) 
INNER JOIN       stages ON course.id_stage = stages.ID) 
INNER JOIN     student ON Absence.student_id = student.ID AND stages.ID = student.stage_id
GROUP BY Absence.date_, stages.name, course.course_name, student.name

Answer 2

What table contains the field "Absence.date_" ? And you do not need to specify "Inner" (or Natural for that matter).

When using aggregate functions (Count(), Sum(), ect) your group by must contain the same list of fields as your select statement. And that error states that either Absence.date_ does not exist as a field in any of the tables in the from clause. But, you have no Group By statement in your query.