SQL Server T-SQL not returning results with no error - this should work right? - sql

Question

I am trying to find something that does not match in 2 tables, this should be easy, now this works fine.
Select *
from Shop_Import SI
where SI.productID not in (SELECT productref FROM Shop_Import_Cats)
But this is the SQL I need to use, but it just does not return the 1 result that the above does:
SELECT
'Insert into Shop_Import_Cats values ('
+ CAST(p.ProductID AS VARCHAR) + ','
+ CAST(c.CategoryID AS VARCHAR) + ','
+ CAST(SI.ProductID AS VARCHAR) + ',getdate())
FROM
NB_Store_Products p
JOIN
NB_Store_ProductLang pl ON p.ProductID = pl.ProductID
JOIN
Shop_Import SI ON p.ProductRef = SI.ProductID
JOIN
NB_Store_CategoryLang CL ON SI.Primary_Category = CL.CategoryName
JOIN
NB_Store_Categories C ON CL.CategoryID = C.CategoryID
JOIN
Shop_Import_Cats SIC ON SI.ProductID = SIC.productref
WHERE
SI.ProductID NOT IN (SELECT SIC.productref
FROM Shop_Import_Cats SIC)
Based on advice here I tried this swapping the tables around and left joins to no avail - it returns null but should return one result.
Select 'Insert into Shop_Import_Cats values (' + CAST(p.ProductID as varchar) + ',' + CAST(c.CategoryID as varchar) + ',' + CAST(SI.ProductID as varchar) + ',getdate())'
from Shop_Import SI
left join NB_Store_Products P on SI.ProductID=p.ProductRef
left join NB_Store_ProductLang pl on p.ProductID=pl.ProductID
left join NB_Store_CategoryLang CL on SI.Primary_Category=CL.CategoryName
left join NB_Store_Categories C on CL.CategoryID=C.CategoryID
left join Shop_Import_Cats SIC on SI.ProductID=SIC.productref
where SI.ProductID not in (SELECT SIC.productref FROM Shop_Import_Cats SIC)
What am I doing wrong?

Answer 1

Try this instead:
SELECT
'Insert into Shop_Import_Cats values ('
+ CAST(coalesce(p.ProductID,' ') AS VARCHAR) + ','
+ CAST(coalesce(c.CategoryID,' ') AS VARCHAR) + ','
+ CAST(coalesce(SI.ProductID,' ') AS VARCHAR) + ',getdate())
from (
select
ProductID,
Primary_Category
/* insert any additional required columnx here */
from Shop_Import SI
where SI.ProductID not in (SELECT SIC.productref FROM Shop_Import_Cats SIC)
) SI
left join NB_Store_Products P on SI.ProductID = p.ProductRef
left join NB_Store_ProductLang pl on p.ProductID = pl.ProductID
left join NB_Store_CategoryLang CL on SI.Primary_Category = CL.CategoryName
left join NB_Store_Categories C on CL.CategoryID = C.CategoryID
left join Shop_Import_Cats SIC on SI.ProductID = SIC.productref
Now the WHERE condition will be executed on the same relvar as in the working example. I suspect that a null value is invoking 3-valued logic and propagating an UNKNOWN into a null record-set.
** edit Needed to add the SI to the 'from Shop_Import'

Answer 2

You just need to remove Shop_import_cats from the join:
Select 'Insert into Shop_Import_Cats values (' + CAST(p.ProductID as varchar) + ',' + CAST(c.CategoryID as varchar) + ',' + CAST(SI.ProductID as varchar) + ',getdate())'
from Shop_Import SI
left join NB_Store_Products P on SI.ProductID=p.ProductRef
left join NB_Store_ProductLang pl on p.ProductID=pl.ProductID
left join NB_Store_CategoryLang CL on SI.Primary_Category=CL.CategoryName
left join NB_Store_Categories C on CL.CategoryID=C.CategoryID
where SI.ProductID not in (SELECT SIC.productref FROM Shop_Import_Cats SIC)