sql - 为 oracle 创建视图时出现语法错误

Question

我的查询：

CREATE VIEW SOME_VIEW2 AS 
(
  SELECT to_char(tbl_albums.album), COUNT(tbl_songs.id) AS "Songs in album"
  FROM tbl_songs 
  LEFT JOIN tbl_albums 
  ON tbl_songs.album_id = tbl_albums.id
  LEFT JOIN tbl_bands
  ON tbl_albums.band_id = tbl_bands.id
  WHERE to_char(LOWER(TRIM(tbl_bands.band))) = 'metallica'
  GROUP BY to_char(tbl_albums.album)
);

我得到的错误：

命令行错误：10 列：12 错误报告：SQL 错误：ORA-00998：必须使用列别名 00998 命名此表达式。00000 -“必须使用列别名命名此表达式”

这不起作用，但是我以前尝试过这个：

CREATE VIEW SOME_VIEW AS 
(
  SELECT * FROM tbl_albums
);

这很好用，想问一下，第一次查询有什么问题。

Answer 1

所有列都必须在视图中命名。由于您有一个计算列，即

to_char(tbl_albums.album)

你需要给它一个名字，像这样：

to_char(tbl_albums.album) "Album"

Answer 2

试试这个查询：

CREATE VIEW SOME_VIEW2 (album , SongsInAlbum) AS 
(
  SELECT q.alb,q.counter FROM
  (SELECT to_char(tbl_albums.album) as alb, rownum as counter
  FROM tbl_songs 
  LEFT JOIN tbl_albums 
  ON tbl_songs.album_id = tbl_albums.id
  LEFT JOIN tbl_bands
  ON tbl_albums.band_id = tbl_bands.id
  WHERE to_char(LOWER(TRIM(tbl_bands.band))) = 'metallica')q
);