将sql语句组合为单个语句

我有4个表，比如A、B、C、D。

"D"有两列"id"answers"Cid"

"C"有两列"id"answers"Bid"

"B"有两列"id"answers"Aid"

如果我想得到"Cid"，我做"SELECT Cid FROM D where id = value which I enter"。

如果我想得到"出价"，我做"SELECT Bid from C where id = result of Cid from above query"。

如果我想得到"援助"，我会做"SELECT Aid from B where id =result is Bid from above query"。

正如您所看到的，这些表是相互关联的。

如何通过组合上述SQL语句直接获得"Aid"；如何在单个SQL语句中获得"Aid"？

    select tb.Aid
      from D td
inner join C tc ON ( tc.id = td.Cid )
inner join B tb ON ( tb.id = tc.Bid )
     where d.id = :value
         ;

SELECT A.id
FROM D
JOIN C ON D.Cid = C.id
JOIN B on C.Bid = B.id
JOIN A on B.Aid = A.id
WHERE D.id = 'foo';