加入ORA-00904

Question

我试图创建以下视图：

CREATE OR REPLACE VIEW AlbumDistribution AS
  SELECT Album.Album_ID,
         Album.title,
         HasTrack.tracked,
         FinishedTrack.released_title,
         SUBSTR(Album.Album_ID, -1) is_distributed_as
    FROM Album A
    JOIN HasTrack HT 
      ON HT.Album_ID = A.Album_ID 
    JOIN FinishedTrack FT
      ON HasTrack.OriginatesFrom = FT.OriginatesFrom
     AND HasTrack.tracked = FT.version;

但是我得到了ORA-00904错误：

 ERROR at line 6:
 ORA-00904: "HASTRACK"."TRACKED": invalid identifier

这让我感到非常困惑，因为我以前引用过HasTrack.tracked，而且没有错误。如果更改语句的顺序，将HasTrack.OriginatesFrom = FT.OriginatesFrom放在最后，则得到相同的错误，但对于HasTrack.OriginatesFrom则是如此。

Answer 1

您可以为此表和其他表定义别名。您需要在整个查询过程中使用别名：

CREATE OR REPLACE VIEW AlbumDistribution AS
    SELECT A.Album_ID, A.title, HT.tracked,
           FT.released_title, SUBSTR(A.Album_ID, -1) is_distributed_as
    FROM Album A JOIN
         HasTrack HT
         ON HT.Album_ID = A.Album_ID JOIN
         FinishedTrack FT
         ON HT.OriginatesFrom = FT.OriginatesFrom AND
            HT.tracked = FT.version;