Question

我一直在网上搜索，甚至在Stackoverflow有关此问题的问题中，但无法收到任何相关回复。我在下面显示的SQL查询，

SELECT Scania.GensetType
    , Scania.EngineType
    , Scania.Engine60Hz
    , Scania.Alternator
    , Scania.PriceEur 
FROM Scania 
LEFT JOIN NordhavnGenset 
    ON Scania.GensetType=NordhavnGenset.Alternator 
WHERE (NordhavnGenset.MaxKva='46') 
    and (Generator.Alternator='ECP34-1LN/4') 
    and (insulation.Insulation='F (90ºC/45ºC)') 
    and (Klasse.Klasse='KRS\r') 
    and (airinletfilter.AirInletFilter='No') 
    and (Ip.IP='IP23');

始终返回以下错误消息，并且我已多次检查该列中是否存在此列！

#1054 - Unknown column 'Generator.Alternator' in 'where clause'

但是，如果我通过停在第一个Where子句来执行查询，则会显示结果

SELECT Scania.GensetType
    , Scania.EngineType
    , Scania.Engine60Hz
    , Scania.Alternator
    , Scania.PriceEur 
FROM Scania 
LEFT JOIN NordhavnGenset 
    ON Scania.GensetType=NordhavnGenset.Alternator 
WHERE (NordhavnGenset.MaxKva='46');

新查询

    SELECT  Scania.GensetType, Scania.EngineType, Scania.Engine60Hz, Scania.Alternator, Scania.PriceEur
FROM Scania  
LEFT JOIN NordhavnGenset
    ON Scania.GensetType=NordhavnGenset.Alternator 
LEFT JOIN Generator
    ON Scania.Alternator=Generator.Alternator
LEFT JOIN Insulation 
    ON NordhavnGenset.Insulation=Insulation.Insulation
LEFT JOIN Klasse
    ON NordhavnGenset.Class=Klasse.Class
LEFT JOIN AirInletFilter
    ON NordhavnGenset.AirInletFilter=AirInletFilter.AirInletFilter
LEFT JOIN IP
    ON NordhavnGenset.Ip=IP.IP
WHERE (NordhavnGenset.MaxKva='46') and (Generator.Alternator='ECP34-1LN/4') and (Insulation.Insulation='F (90ºC/45ºC)') and (Klasse.Klasse='KRS\r') and (AirInletFilter.AirInletFilter='No') and (IP.IP='IP23');

Answer 1

您似乎没有加入名为Generator的桌子。除非您WHERE，否则您无法在JOIN子句中使用该表。

如果您向JOIN添加Generator，则可以在WHERE子句中使用它。

SELECT *
FROM Scania 
LEFT JOIN NordhavnGenset 
    ON Scania.GensetType=NordhavnGenset.Alternator 
LEFT JOIN Generator 
    ON ....
WHERE (Generator.Alternator='ECP34-1LN/4') ...

您的WHERE子句中还有其他表格不是JOINed，因此您还需要添加这些表格。

Answer 2

错误的原因是您没有加入WHERE子句中使用的表。

以下内容总是会出错 -

and (Generator.Alternator='ECP34-1LN/4') 
and (insulation.Insulation='F (90ºC/45ºC)') 
and (Klasse.Klasse='KRS\r') 
and (airinletfilter.AirInletFilter='No') 
and (Ip.IP='IP23');

您需要将表连接起来，或者表的别名应该是'。'之前的名称。

Answer 3

您未在联接中包含Generator表。可以添加它，也可以表示NordhavnGenset.Alternator而不是Generator.Alternator

在SQL WHERE子句中使用多个条件

3 个答案: