我有以下 MySQL 查询:
SELECT p.*,
IF(COUNT(ms.PropertyID) > 0,1,0) AS Contacted,
pm.MediaID,
date_format(p.AvailableFrom, '%d %b %Y') AS 'AvailableFrom',
astext(pg.Geometry) AS Geometry
FROM property p, propertygeometry pg
JOIN shortlist sl ON sl.PropertyID = p.id AND sl.MemberID = 384216
LEFT JOIN message ms ON ms.PropertyID = p.id AND ms.SenderID = 384216
LEFT JOIN property_media pm ON pm.PropertyID = p.id AND pm.IsPrimary = 1
WHERE p.paused = 0
AND p.PropertyGeometryID = pg.id
GROUP BY p.id
我收到此错误:
#1054 - “on 子句”中存在未知列“p.id”
据我所知，查询看起来是正确的，知道可能出了什么问题吗？
最佳答案
不要混合使用 ANSI-89 样式和 ANSI-92 样式连接。它们具有不同的优先级，这可能会导致令人困惑的错误，这就是这里发生的情况。您的查询将被解释如下:
FROM property p, (
propertygeometry pg
JOIN shortlist sl ON sl.PropertyID = p.id AND sl.MemberID = 384216
...
)
在上面，在考虑逗号样式连接之前，首先评估使用 JOIN 关键字的连接。此时表 p 尚未声明。
来自MySQL manual :
However, the precedence of the comma operator is less than of INNER JOIN, CROSS JOIN, LEFT JOIN, and so on. If you mix comma joins with the other join types when there is a join condition, an error of the form Unknown column 'col_name' in 'on clause' may occur. Information about dealing with this problem is given later in this section.
我建议始终使用 ANSI-92 样式连接，即使用 JOIN 关键字:
SELECT p.*,
IF(COUNT(ms.PropertyID) > 0,1,0) AS Contacted,
pm.MediaID,
date_format(p.AvailableFrom, '%d %b %Y') AS 'AvailableFrom',
astext(pg.Geometry) AS Geometry
FROM property p
JOIN propertygeometry pg ON p.PropertyGeometryID = pg.id
JOIN shortlist sl ON sl.PropertyID = p.id AND sl.MemberID = 384216
LEFT JOIN message ms ON ms.PropertyID = p.id AND ms.SenderID = 384216
LEFT JOIN property_media pm ON pm.PropertyID = p.id AND pm.IsPrimary = 1
WHERE p.paused = 0
GROUP BY p.id
相关:
关于sql - MySQL ON 子句中的未知列，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/55615455/