select t1.*, t2.*
from table t1 join table t2 on (((t1.d_beg >= t2.d_beg and t1.d_beg <= t2.d_end) or (t1.d_end >= t2.d_beg and t1.d_end <= t2.d_end)) and t1.id_sotr <> t2.id_sotr)
Для правильного вопроса надо знать половину ответа
SELECT *
FROM `table` AS `t1`
JOIN `table` AS `t2` ON `t1`.`user_id` < `t2`.`user_id`
AND `t1`.`date_start` <= `t2`.`date_end` AND `t2`.`date_start` <= `t1`.`date_end`
