mysql - Duplication removal with group by or distinct -

here have query scenario, explained scope in inline comments:

select      -- selecting both entity ids     entity_a.id entity_a_id,      entity_b.id entity_b_id,     concat(entity_a.id, entity_b.id) `key`  `entity_b`   -- following few 1 many relations match entity b inner join `entity_b_function` on      `entity_b`.`id` = `entity_b_function`.`entity_b_id`  inner join `entity_b_category` on      `entity_b`.`id` = `entity_b_category`.`entity_b_id`  inner join `entity_b_scope` on      `entity_b`.`id` = `entity_b_scope`.`entity_b_id`   inner join `entity_a` on      `entity_a`.`category_id` = `entity_b_category`.`category_id` ,      `entity_a`.`scope_id` = `entity_b_scope`.`scope_id`  inner join `entity_a_function` on      `entity_b_function`.`function_id` = `entity_a_function`.`function_id`    -- pivot of entity , b -- making sure matching entities related in pivot left join `entity_a_b_pivot` on      `entity_a_b_pivot`.`entity_a_id` = `entity_a`.`id` ,      `entity_a_b_pivot`.`entity_b_id` = `entity_b`.`id`        -- need matching entities not yet related in pivot     `entity_a_b_pivot`.`id` null ,      -- when both entities active in system     `entity_b`.`status` = 1 ,      `entity_a`.`status` = 1  limit 5000; 

currently resulted below:
(pointed items duplication due joins of 1 many relations)

entity_a_id,    entity_b_id     key     1               1           11 >   1               1           11     1               2           12     2               1           21     2               2           22 >   2               2           22 

here, if either use group key or distinct(key) eliminate duplicates, query processing stuck forever 100% cpu usage without these blink return 5k records 90% duplicates.

how optimize query distinct results?

how add distinct @ beginning of select list?

select      -- selecting both entity ids     distinct     entity_a.id entity_a_id,      entity_b.id entity_b_id,     concat(entity_a.id, entity_b.id) `key`  `entity_b`   -- following few 1 many relations match entity b inner join `entity_b_function` on      `entity_b`.`id` = `entity_b_function`.`entity_b_id`  inner join `entity_b_category` on      `entity_b`.`id` = `entity_b_category`.`entity_b_id`  inner join `entity_b_scope` on      `entity_b`.`id` = `entity_b_scope`.`entity_b_id`   inner join `entity_a` on      `entity_a`.`category_id` = `entity_b_category`.`category_id` ,      `entity_a`.`scope_id` = `entity_b_scope`.`scope_id`  inner join `entity_a_function` on      `entity_b_function`.`function_id` = `entity_a_function`.`function_id`    -- pivot of entity , b -- making sure matching entities related in pivot left join `entity_a_b_pivot` on      `entity_a_b_pivot`.`entity_a_id` = `entity_a`.`id` ,      `entity_a_b_pivot`.`entity_b_id` = `entity_b`.`id`        -- need matching entities not yet related in pivot     `entity_a_b_pivot`.`id` null ,      -- when both entities active in system     `entity_b`.`status` = 1 ,      `entity_a`.`status` = 1  limit 5000;