SQL查询：通过2列联接选择

Question

In SQL Server 2014 ...

I am trying to find the rows in table 'new' that do not exist in table 'old'. I want to take these new rows and stuff them into a third table that I create. Table 'new' has a primary key composed of two columns, MakeId and ModelId. The following SQL runs, but gives me vastly too many rows. Obviously, I am doing something wrong.

select 
   new.MakeId     ,
   new.MageMakeId ,
   new.ModelId    ,
   new.MageModelId
into BiUpdater..TranslateModel 
from Mage_Production..TranslateModel new
   left outer join BiLoader..TranslateModel old0 on new.MakeId  = old0.MakeId 
   left outer join BiLoader..TranslateModel old1 on new.ModelId = old1.ModelId 
go

Answer 1

My guess is that you want only one join using both columns:

select new.MakeId, new.MageMakeId, new.ModelId, new.MageModelId
into BiUpdater..TranslateModel 
from Mage_Production..TranslateModel new left outer join
     BiLoader..TranslateModel old
     on new.MakeId = old.MakeId and new.ModelId = old.ModelId
where old.MakeId is null;

More importantly, though, you need the where clause to get the non-matches.

EDIT:

If you are looking for rows that don't match either MakeId or ModelId , then perhaps this is really what you want:

select new.MakeId, new.MageMakeId, new.ModelId, new.MageModelId
into BiUpdater..TranslateModel 
from Mage_Production..TranslateModel new left outer join
     BiLoader..TranslateModel old1
     on new.MakeId = old1.MakeId left join
     BiLoader..TranslateModel old2
     on new.ModelId = old2.ModelId
where old1.MakeId is null and old2.ModelId is null;

You might want an or instead of and , in which case use select distinct .

Answer 2

There is a SQL statement called EXCEPT that does this. here is a link- http://msdn.microsoft.com/en-us/library/ms188055.aspx

Your right hand table would be 'new' and your left hand table would be 'old'.

select *
into BiUpdater..TranslateModel  
from (
select new.*
from Mage_Production..TranslateModel new

EXCEPT

select old.*
from BiLoader..TranslateModel old
)

Alternatively you could use a left join to do this:

select new.*
into BiUpdater..TranslateModel 
from Mage_Production..TranslateModel new left join BiLoader..TranslateModel old
on new.MakeId = old.MakeId and new.ModelId = old.ModelId
where old.MakeId is null