你可以按照你的建议去做，使用in（）

FROM T1
FULL OUTER JOIN T2
 ON(T1.id = T2.id)
FULL OUTER JOIN T3
 ON(T3.ID IN(T2.id,T1.id))

或者我认为你可以通过工会来做到这一点（取决于你需要什么）：

SELECT * FROM 
    (SELECT name,id from T1
    UNION
    SELECT name,id from T2) x
FULL OUTER JOIN T3
   ON(t3.id = x.id)

通常，完全外部连接的链的行为与预期不完全相同。一个替代品使用 left join . 当一个表具有您所需要的所有id时，这种方法效果最好。但你也可以构造：

from (select id from t1 union
      select id from t2 union
      select id from t3
     ) ids left join
     t1
     on ids.id = t1.id left join
     t2
     on ids.id = t2.id left join
     t3
     on ids.id = t3.id

注意，第一个子查询通常可以被表替换。如果您有这样一个表，您可以在 where 条款：

from ids left join
     t1
     on ids.id = t1.id left join
     t2
     on ids.id = t2.id left join
     t3
     on ids.id = t3.id
where t1.id is not null or t2.id is not null or t3.id is not null

SELECT COALESCE(X.id,t3.id) AS id, *-- specific columns here instead of the *
FROM 
    (
       SELECT COALESCE(t1.id,t2.id) AS id, * -- specific columns here instead of the *
       FROM T1 FULL OUTER JOIN T2 on T1.id = T2.id
    ) AS X
    FULL OUTER JOIN T3 on X.id = t3.id