Select not null column in full join postgresql - postgresql

Question

I have 3 tables:
with current_exclusive as(
select id_station, area_type,
count(*) as total_entries
from c1169.data_cashier
where id_station IN(2439,2441,2443,2445,2447,2449) and date >= '2017-10-30' and date <= '2017-12-30'
group by id_station, area_type
), current_table as(
select id_station, area_type,
sum(total_time) filter (where previous_status = 1) as total_time
from c1169.data_table
where id_station IN(2439,2441,2443,2445,2447,2449) and date >= '2017-10-30' and date < '2017-12-30'
group by id_station, area_type
), current_cashier as(
select id_station, area_type,
sum(1) as total_transactions
from c1169.data_cashier
where id_station IN(2439,2441,2443,2445,2447,2449) and date >= '2017-10-30' and date < '2017-12-30'
group by id_station, area_type
)
select *
from current_exclusive
full join current_table on current_exclusive.id_station = current_table.id_station and current_exclusive.area_type = current_table.area_type
full join current_cashier on current_exclusive.id_station = current_cashier.id_station and current_exclusive.area_type = current_cashier.area_type
and the result is:
but my expected result is:
Are there any way to select * and show the expected result? Because when I do full join then id_station and area_type can be null in some tables, so it very hard to choose which column is not null.
Like: select case id_station is not null then id_station else id_station1 end, but I have up to 10 tables so can not do in select case

Answer 1

Use USING, per the documentation:
USING ( join_column [, ...] )
A clause of the form USING ( a, b, ... ) is shorthand for ON left_table.a = right_table.a AND left_table.b = right_table.b .... Also, USING implies that only one of each pair of equivalent columns will be included in the join output, not both.
select *
from current_exclusive
full join current_table using (id_station, area_type)
full join current_cashier using (id_station, area_type)

Answer 2

You cannot accomplish anything if you insist on using select *, since you are getting the values from different tables.
The option you have is to include a COALESCE block which gives you the first non-null value from the list of columns.
So, you could use.
select COALESCE( current_exclusive.id_station, current_table.id_station, current_cashier.id_station ) as id_station ,
COALESCE( current_exclusive.area_type , current_table.area_type, current_cashier.area_type ) as area_type ,.....
...
from current_exclusive
full join current_table..
...