Is there any way to have a subquery return multiple columns in oracle db? (I know this specific sql will result in an error, but it sums up what I want pretty well)
It's incorrect, but you can try this instead:
select
a.x,
( select b.y from b where b.v = a.v) as by,
( select b.z from b where b.v = a.v) as bz
from a
you can also use subquery in join
select
a.x,
b.y,
b.z
from a
left join (select y,z from b where ... ) b on b.v = a.v
or
select
a.x,
b.y,
b.z
from a
left join b on b.v = a.v