Oracle-重写此查询以不使用子选择的方法？

Question

I'm trying to create a materialized view in Oracle 11.1, which apparently does not support nested selects in a materialized view (Why this is, I haven't been able to figure out).. Is there a way to write this query to work as a materialized view? Thanks!

CREATE MATERIALIZED VIEW MV_Area90DayReport
  NOLOGGING
  CACHE
  BUILD IMMEDIATE 
  REFRESH FAST ON COMMIT 
  AS 
    select
      T.TASKID,
      V.PROJECTID,
      V.VERSIONID,
      T.GOLDDATE,
      P.BUSINESSLAUNCHDATE,
      V.NAME as ProjectName,
      T.NAME as TaskName,
      T.COURSECODE,
      DT.NAME as DeliveryMethod,
      T.DELIVERABLELENGTHHOUR,
      T.DELIVERABLELENGTHMINUTE,
      V.PRIORITY,
      (SELECT MIN(STARTDATE) FROM TPM_TRAININGPLAN WHERE PROJECTID=V.PROJECTID AND TRAININGPLANTYPE='prescribed') as TrainingDeliveryDate,
      (SELECT wm_concat(WORKGROUPID) FROM TPM_PROJECTWORKGROUPS WHERE PROJECTID=V.PROJECTID GROUP BY PROJECTID) as Workgroups,
    from TPM_TASK T
    inner join TPM_PROJECTVERSION V ON (V.PROJECTID = T.PROJECTID AND V.VERSIONID = T.VERSIONID)
    inner join TPM_PROJECT P ON (P.PROJECTID = T.PROJECTID)
    inner join TPM_DOCUMENTTYPE DT ON (DT.DOCUMENTTYPEID = T.DOCUMENTTYPEID);

The error I get is:

>[Error] Script lines: 1-25 -------------------------
 ORA-22818: subquery expressions not allowed here
 Script line 20, statement line 20, column 115 

Answer 1

I believe this is a limitation (that was raised as a bug sometime back), documented here on the Oracle site - http://download.oracle.com/docs/cd/B12037_01/server.101/b10736/basicmv.htm#sthref431

To resolve, you should use JOINS rather than subqueries.

Answer 2

Try the following query:

select
  T.TASKID,
  V.PROJECTID,
  V.VERSIONID,
  T.GOLDDATE,
  P.BUSINESSLAUNCHDATE,
  V.NAME as ProjectName,
  T.NAME as TaskName,
  T.COURSECODE,
  DT.NAME as DeliveryMethod,
  T.DELIVERABLELENGTHHOUR,
  T.DELIVERABLELENGTHMINUTE,
  V.PRIORITY,
  TP.TrainingDeliveryDate,
  WG.Workgroups,
from TPM_TASK T
inner join TPM_PROJECTVERSION V ON (V.PROJECTID = T.PROJECTID AND V.VERSIONID = T.VERSIONID)
inner join TPM_PROJECT P ON (P.PROJECTID = T.PROJECTID)
inner join TPM_DOCUMENTTYPE DT ON (DT.DOCUMENTTYPEID = T.DOCUMENTTYPEID)
left join (
  SELECT PROJECTID, MIN(STARTDATE) as TrainingDeliveryDate
  FROM TPM_TRAININGPLAN
  WHERE TRAININGPLANTYPE='prescribed'
  GROUP BY PROJECTID
) TP on TP.PROJECTID=V.PROJECTID
left join (
  SELECT PROJECTID, wm_concat(WORKGROUPID) as Workgroups
  FROM TPM_PROJECTWORKGROUPS
  GROUP BY PROJECTID
) WG on WG.PROJECTID=V.PROJECTID