SQL - Foreign Key Constraint Error with Update Statement

Question

I am Trying to update my table (product) columns - ProductID(FK) and ProductType(FK). These two column has relation with MProduct table's column MProductID(PK) and MProductType(PK).

I am trying to update

ProductID       ProductType
9999            11
9999            12

But I got the following error

The UPDATE statement conflicted with the FOREIGN KEY constraint "FKHCR_MProduct".
The conflict occurred in database "XXXX", table "dbo.MProduct".

I checked with MProduct table, It has all the valid records for look up. I can not change my Table Structure.

I tried this Query too

Select ProductID,ProductType
from dbo.Product P
Left Join dbo.MProduct M on M.ProductID = P.ProductID
   and M.ProductType = P.ProductType
where M.ProductType is null
   and M.ProductID is null

and there is No Output, means there is No Null Data Inside the Look up table.

Solution

In all the possible scenarios, you are either trying to insert a NULL value in your table or a value that does not exist in the reference table.

Most of the time, it is because you are trying to insert the NULL value in the field.