sql 问题的求助

SELECT
t1.name,
t2.course_id,
t2.count_class_session,
t2.sum_duration,
t4.id,
t4.rowNo 
	FROM
`tb_course` t1
LEFT JOIN ( SELECT course_id, count(*) count_class_session, sum( duration ) sum_duration FROM tb_class_session GROUP BY course_id ) t2 ON t2.course_id = t1.id
LEFT JOIN tb_learn_record t3 ON t3.course_id = t1.id
LEFT JOIN (
SELECT
	a.id,
	( @rowNum := @rowNum + 1 ) AS rowNo 
FROM
	tb_class_session a,
	( SELECT ( @rowNum := 0 ) ) b 
ORDER BY
a.sequence_no ASC 
) t4 ON t4.id = t3.class_session_id

求助 如何 把 t1.id 传入 SELECT a.id, ( @rowNum := @rowNum + 1 ) AS rowNo FROM tb_class_session a, ( SELECT ( @rowNum := 0 ) ) b ORDER BY a.sequence_no ASC 内