MYSQL GROUP_CONCAT INCLUDE NULL

Question

I use this code to group the equipment, but when the id_material has no equipment the id_material didn't show.

select
material.id_material, 
material.mat_part_number, 
group_concat(distinct equipment.equipment_name order by equipment.equipment_name separator ', ') as equipment    
FROM material   
INNER JOIN equipment_list ON material.id_material=equipment_list.PKid_material INNER JOIN equipment ON equipment_list.PKid_equipment=equipment.id_equipment group by id_material;

i want it to appear like this

+-------------+----------------+
| id_material | equipment      |                                                             
+-------------+----------------+
|     1000001 | eq1            |         
|     1000002 | eq1, eq2       |
|     1000003 | eq3            |
|     1000004 |                |                           
+-------------+----------------+

but it only appear this

+-------------+----------------+
| id_material | equipment      |                                                             
+-------------+----------------+
|     1000001 | eq1            |         
|     1000002 | eq1, eq2       |
|     1000003 | eq3            |                        
+-------------+----------------+

where should i put the NULL condition?

Answer 1

I just modified your query, this might help you.

SELECT 
  material.id_material, 
  material.mat_part_number, 
  GROUP_CONCAT(
    DISTINCT equipment.equipment_name 
    ORDER BY 
      equipment.equipment_name SEPARATOR ', '
  ) AS equipment 
FROM 
  material 
  LEFT JOIN equipment_list ON material.id_material = equipment_list.PKid_material 
  LEFT JOIN equipment ON equipment_list.PKid_equipment = equipment.id_equipment 
GROUP BY 
  id_material;