Question

I have a database table like the one mentioned below.

id    | lecture            | subject_id | date       | is_deleted
------|--------------------|------------|------------|-----------
 1    | Introduction       | 1          | 2012-08-10 | 0   
 2    | Structure          | 2          | 2012-08-15 | 1   
 3    | Introduction       | 2          | 2012-08-12 | 0   
 4    | Functions          | 1          | 2012-08-14 | 1   
 5    | Material           | 2          | 2012-08-18 | 0   
 6    | Requirements       | 1          | 2012-08-16 | 0   
 7    | Analysis           | 1          | 2012-08-11 | 0

I need to make a view out of this table (Lecture), which will display a row no. (flow no.) for each subject ordered by date, removing is_deleted = 1 rows. Simply, making a flow no. for each lecture in a particular subject ordered by date only with not deleted lectures. So, the view made by above data will look like the following.

flow_no | id   | date       | lecture            | subject_id 
--------|------|------------|--------------------|------------
 1      | 1    | 2012-08-10 | Introduction       | 1          
 2      | 7    | 2012-08-11 | Analysis           | 1          
 3      | 6    | 2012-08-16 | Requirements       | 1          
 1      | 3    | 2012-08-12 | Introduction       | 2          
 2      | 5    | 2012-08-18 | Material           | 2          

I tried to do this in several ways and everything failed. It’s highly appreciated if someone could help me to resolve this. (mysql)

Answer 1

I found the answer by the support of another online forum’s member. The following will give the exact result required. If there is any same Lecture.date rows it generates flow_no in Lecture.id order for those rows.

SELECT id, lecture, Lecture.subject_id, date, c,
 (SELECT COUNT(subject_id) + 1 FROM Lecture AS l
  WHERE l.subject_id = Lecture.subject_id
  AND (l.date < Lecture.date OR (l.date = Lecture.date AND l.id < Lecture.id))
  AND is_deleted != 1
 ) AS flow_no
FROM Lecture
INNER JOIN
(
 SELECT subject_id, COUNT(subject_id) AS c
 FROM Lecture
 WHERE is_deleted != 1
 GROUP BY subject_id
) AS counts
ON Lecture.subject_id = counts.subject_id
WHERE is_deleted != 1
ORDER BY subject_id, date;