Question

第一个查询正在运行：

SELECT video.seller from video;

第二个不是：

SELECT SQL_CALC_FOUND_ROWS *,
       t.name as tname
FROM video, type as t 
INNER JOIN user 
ON video.seller = user.id 
WHERE video.type2 = t.id 
AND thumbnail_blobKey != '' 
AND disabled = 0 
AND is_reel = 0 
AND price!= 0 
AND video.type != 4  
GROUP BY video.id 
ORDER BY video.id DESC LIMIT 0, 10

错误：未知栏＆＃39; video.seller＆＃39;在＆＃39; on条款＆＃39;

Answer 1

这是一个有趣的例子。格式更好：

SELECT SQL_CALC_FOUND_ROWS *, t.name as tname
FROM video, type as t INNER JOIN
     user
     ON video.seller = user.id
WHERE video.type2 = t.id AND
     thumbnail_blobKey != '' AND disabled = 0 AND is_reel = 0 AND price!= 0 AND video.type != 4 
GROUP BY video.id
ORDER BY video.id DESC
LIMIT 0, 10

问题是由于video，from子句的其余部分无法理解,的列。这就是逗号的工作原理。有趣的是，只需将,替换为逻辑等效cross join即可解决此问题：

SELECT SQL_CALC_FOUND_ROWS *, t.name as tname
FROM video cross join type as t INNER JOIN
     user
     ON video.seller = user.id
WHERE video.type2 = t.id AND
     thumbnail_blobKey != '' AND disabled = 0 AND is_reel = 0 AND price!= 0 AND video.type != 4 
GROUP BY video.id
ORDER BY video.id DESC
LIMIT 0, 10

这在documentation中有解释，原因是优先顺序。逗号的优先级低于cross join。因此，表达式中的连接被评估为“视频连接（类型连接用户）”。由于首先解释了第二个连接，因此video中的列不可知。

但是，表上确实有一个连接，所以最好写成：

SELECT SQL_CALC_FOUND_ROWS *, t.name as tname
FROM video join
     type t
     on video.type2 = t.id INNER JOIN
     user
     ON video.seller = user.id
WHERE thumbnail_blobKey != '' AND disabled = 0 AND is_reel = 0 AND price!= 0 AND video.type != 4 
GROUP BY video.id
ORDER BY video.id DESC
LIMIT 0, 10

Answer 2

正如现在所写的那样，您正在尝试加入表格type和user，其条件为video.seller = user.id。由于video.seller是一个表type或user的列，因此您有错误。

更改为以下内容将删除此错误：

    SELECT SQL_CALC_FOUND_ROWS *,
       t.name AS tname
FROM video
INNER JOIN USER ON video.seller = USER.id,
                                       TYPE AS t
WHERE video.type2 = t.id
  AND thumbnail_blobKey != ''
  AND disabled = 0
  AND is_reel = 0
  AND price!= 0
  AND video.TYPE != 4
GROUP BY video.id
ORDER BY video.id DESC LIMIT 0,
                             10

MySQL Unknown列on子句

2 个答案: