Strange / esoteric join syntax

Question

I\'ve been provided this old SQL code (table names changed) to replicate, and the JOIN syntax isn\'t something I\'ve seen before, and is proving hard to google:

Answer 1

I ran it by a colleague who figured it out:

select 

from A

inner join B
on A.ID = B.A_ID

inner join ( C  -- put a bracket here...

inner join D
ON C.C_ID = D.C_ID

) -- and one here

ON B.C_ID = D.C_ID

or to format it a little nicer:

select 

from A

inner join B
on A.ID = B.A_ID

inner join ( 
    C
    inner join D
    ON C.C_ID = D.C_ID
)
ON B.C_ID = D.C_ID

I wasn't familiar with this kind of "sub-join" (I don't know what it's called), but this is much more readable and clear