Question

I am at the task of joining 3 tables:
Task, Unit, and Building.

The task table has a column for a unit and a column for a building.
Any single task is assigned to only a building OR a unit, never both.
Thus one column in every record is always null. There are 6100 records in the task table.

when I use this JOIN:

select * from task t
join building b on b.id = t.building_id;

I get 628 rows. This is the correct total of building tasks.

When I use this JOIN

select * from active_task at
inner join unit_template ut on ut.id = at.unit_template_id

I get 5472 rows. This is the correct number of unit tasks.
If I add them up 5472+628 =6100 this is the correct # of rows in the task table.

When I run this Query:

select * from task t
inner join unit ut on ut.id = t.unit_id
inner join building bt on bt.id = t.building_id

I get zero rows. I need my query to retrieve 6100 rows.
Any help would be appreciated.

Answer 1

Try a left join:

select * from task t
left join unit ut on ut.id = t.unit_id
left join building bt on bt.id = t.building_id