Cant insert the value NULL into column

I'm trying to modify the data type in a field on a table. I rec'd this message:
Unable to modify tblship_sched
Can't insert the value NULL into column mfg_qty table qc.dbo.Tmp_tblship_sched; Column doesn't allow nulls.
Insert fails.

What is or where is the Tmp table?

Thank you.I am not sure what you mean when you ask where the table is.

SELECT * FROM SYSOBJECTS WHERE NAME = 'Tmp_tblship_sched'

If the table exists then I suggest you check the column constraint for the table in question. Looks like it has a NOT NULL constraint.

You can disable it for your insert.

Good Luck!