Nullable Key Column

harshada · Post by **harshada** » Wed Feb 01, 2012 3:01 am

Can a key column be nullable (nullable =yes). In one of the jobs I can see this. More than one columns are key columns and out of those all are nullable =No, except one column, still the job is running fine.

Want to understand how this is working.
Also, can we apply a if 'isnull' function on the key column where
nullable =yes as well as key column where nullable = no

jwiles · Post by **jwiles** » Wed Feb 01, 2012 6:54 am

Yes, key columns can be nullable. NULLs are effectively another value for a column and you're still bound to any unique constraints that are in effect for your data source/target.

Null-handling logic in the modify and transformer stages is meant to be applied only to nullable columns. You will receive warnings if you try to use IsNull() on a non-nullable column.

Regards,

harshada · Post by **harshada** » Wed Feb 01, 2012 7:33 am

Thanks.

I expected the same. But now the job is aborting with error

Using "null" conversion with non-nullable input
APT_CombinedOperatorController(0),0: Null handling function called on a not nullable field.

for the only column which is key and nullable is Yes and not for the rest of the key columns which are already nullable=no. This is strange.

ray.wurlod · Post by **ray.wurlod** » Wed Feb 01, 2012 3:05 pm

Just get it right. If the data can contain nulls, mark them as nullable and handle the nulls. If the data can not contain nulls, do neither of these things.