用UNION和LEFT JOIN选择

Question

嗨，大家好，我一直在尝试对我的网站搜索工具进行此sql搜索查询，它应该按相关性进行搜索和排序。 它在没有左联接的情况下工作，而我无法在左联接的情况下工作。 这是SQL查询。

SELECT bl_albums.*, bl_bands.name as bandname, bl_bands.id as bandid, 
       bl_bands.bandpage as bandpage, sum(relevance)
FROM bl_albums 
LEFT JOIN(
  SELECT  bl_albums.*, bl_bands.name as bandname, bl_bands.id as bandid, 
          bl_bands.bandpage as bandpage,10 AS relevance 
  FROM bl_albums 
  WHERE bl_albums.name like 'Camera'
  UNION
  SELECT bl_albums.*, bl_bands.name as bandname, bl_bands.id as bandid, 
         bl_bands.bandpage as bandpage, 7 AS relevance 
  FROM bl_albums 
  WHERE bl_albums.name like 'Camera%'
  UNION
  SELECT  bl_albums.*, bl_bands.name as bandname, bl_bands.id as bandid, 
          bl_bands.bandpage as bandpage, 5 AS relevance 
  FROM bl_albums 
  WHERE bl_albums.name like '%Camera'
  UNION
  SELECT bl_albums.*, bl_bands.name as bandname, bl_bands.id as bandid, 
         bl_bands.bandpage as bandpage, 2 AS relevance 
  FROM bl_albums 
  WHERE bl_albums.name like '%Camera%'
)  bl_bands on bl_albums.bandid = bl_bands.id
GROUP BY bl_albums.name
ORDER BY relevance desc

所有表名均正确，所有列名均正确。

Answer 1

您名为“ bl_bands”的子查询没有bl_bands.id，因为所有的联合联接都不包括bl_bands表。 如果我对所有数据的假设正确，请尝试将联接添加到每个联合：

SELECT
    bl_albums.*,
    bl_bands.name as bandname,
    bl_bands.id as bandid, 
    bl_bands.bandpage as bandpage,
    sum(relevance)
FROM
    bl_albums 
    LEFT JOIN(
      SELECT  bl_albums.*, bl_bands.name as bandname, bl_bands.id as bandid, 
              bl_bands.bandpage as bandpage,10 AS relevance 
      FROM bl_albums
        JOIN bl_bands ON bl_bands.id = bl_albums.bandid 
      WHERE bl_albums.name like 'Camera'
      UNION
      SELECT bl_albums.*, bl_bands.name as bandname, bl_bands.id as bandid, 
             bl_bands.bandpage as bandpage, 7 AS relevance 
      FROM bl_albums 
        JOIN bl_bands ON bl_bands.id = bl_albums.bandid
      WHERE bl_albums.name like 'Camera%'
      UNION
      SELECT  bl_albums.*, bl_bands.name as bandname, bl_bands.id as bandid, 
              bl_bands.bandpage as bandpage, 5 AS relevance 
      FROM bl_albums 
        JOIN bl_bands ON bl_bands.id = bl_albums.bandid
      WHERE bl_albums.name like '%Camera'
      UNION
      SELECT bl_albums.*, bl_bands.name as bandname, bl_bands.id as bandid, 
             bl_bands.bandpage as bandpage, 2 AS relevance 
      FROM bl_albums 
        JOIN bl_bands ON bl_bands.id = bl_albums.bandid
      WHERE bl_albums.name like '%Camera%'
    ) bl_bands ON bl_albums.bandid = bl_bands.id
GROUP BY bl_albums.name
ORDER BY relevance desc

看起来您可能已经复制/粘贴了一些SELECT语句/列名，但没有添加需要获得结果的联接。

Answer 2

我认为此查询从未奏效。 内部查询没有任何意义。 例如

SELECT  bl_albums.*, bl_bands.name as bandname, bl_bands.id as bandid, 
      bl_bands.bandpage as bandpage,10 AS relevance 
FROM bl_albums 
WHERE bl_albums.name like 'Camera'

该查询包括许多以bl_bands前缀的字段，但是该表未包含在from语句或联接中。