Oracle Netezza中的子查询

我正在尝试将一个SQL从Oracle11g移植到Netezza

以下是我在Oracle中的查询：

SELECT
    ID, TEACHERID, CLASS, SECTION, MAJOR, SUPERVISOR, COURSE, SCORE, SCOREDATE, 
    (select SCORE from STUDENT_SCORES d2 where d2.ID=d1.ID and d2.SCOREDATE (d1.SCOREDATE)-28 and d1.COURSE=d2.COURSE)  as PRIORSCORE, 
    (d1.SCOREDATE)-28 as PRIORSCOREDT,
    REMCD
FROM 
    STUDENT_SCORES d1
WHERE 
    TEACHERID='T1' AND SCOREDATE=(SELECT MAX(SCOREDATE) FROM STUDENT_SCORES WHERE TEACHERID='T1')

在Netezza中运行此命令时，我收到一个错误：

ERROR:  (2) This form of correlated query is not supported - consider rewriting

如何为Netezza重写此查询？请帮助。

根据Netezza

• 不能在集合操作中使用相关子查询（

  UNION

  、

  INTERSECT

  、

  EXCEPT

  和

  减号

  ）
• 不能将相关子查询与

  GROUP BY

  和

  具有

  子句的聚合一起使用
• 当表达式时，不能在or子句或

  大小写

  /

  中使用相关子查询

• 不能在列表中的

  中使用相关子查询

• 您不能在

  SELECT

  列表中使用相关子查询。
  

重写的查询：（Oracle）（不确定是否使用Netezza语法）

---

我建议您将代码改写为：

select d1.ID, d1.TEACHERID, d1.CLASS, d1.SECTION, d1.MAJOR, d1.SUPERVISOR, d1.COURSE, d1.SCORE, d1.SCOREDATE
,d2.SCORE as PRIORSCORE
,d2.SCOREDATE as PRIORSCOREDT
,d1.REMCD
from STUDENT_SCORES d1 left outer join
(select * from STUDENT_SCORES ss where ss.SCOREDATE = (SELECT MAX(SCOREDATE)-28 FROM STUDENT_SCORES WHERE TEACHERID='T1') d2
on  d1.ID=d2.ID
and d1.COURSE=d2.COURSE
where d1.TEACHERID='T1'
and d1.SCOREDATE = (SELECT MAX(SCOREDATE) FROM STUDENT_SCORES WHERE TEACHERID='T1')

---

您确定

select

子句（

PRIORSCORE

）中的子查询没有返回多行吗？请查找您的答案。您不能在

SELECT

列表中使用相关子查询。Maheswaran Ravishankar是的，我知道我不能使用相关子查询，但我如何为Netezza重写它？您的问题在这里得到了回答，还是仍然有问题？

select d1.ID, d1.TEACHERID, d1.CLASS, d1.SECTION, d1.MAJOR, d1.SUPERVISOR, d1.COURSE, d1.SCORE, d1.SCOREDATE
,d2.SCORE as PRIORSCORE
,d2.SCOREDATE as PRIORSCOREDT
,d1.REMCD
from STUDENT_SCORES d1 left outer join
(select * from STUDENT_SCORES ss where ss.SCOREDATE = (SELECT MAX(SCOREDATE)-28 FROM STUDENT_SCORES WHERE TEACHERID='T1') d2
on  d1.ID=d2.ID
and d1.COURSE=d2.COURSE
where d1.TEACHERID='T1'
and d1.SCOREDATE = (SELECT MAX(SCOREDATE) FROM STUDENT_SCORES WHERE TEACHERID='T1')