SQL conflicted with the FOREIGN KEY constraint

Question

I am trying to run some update scripts on my database and I am getting the following error:

The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_UPSELL_DT_AMRNO_AFMKTG_REF". The conflict occurred in database "ECOMVER", table "dbo.AFFILIATE_MKTG_REF", column 'AMRNO'.

I am running the following script:

ALTER TABLE [dbo].[UPSELL_DATA]  WITH CHECK ADD 
        CONSTRAINT [FK_UPSELL_DT_AMRNO_AFMKTG_REF] FOREIGN KEY
        (
          [AMRNO]
        ) REFERENCES [dbo].[AFFILIATE_MKTG_REF] (
          [AMRNO]
        )
GO

AMRNO is a PK in table AFFILIATE_MKTG_REF.

Also, I tried to create the foreign key relation using the modify table option in SQL Management studio and I got the same error. I am not sure what I should be looking for?

Any suggestions would be greatly appreciated.

Answer 1

You probably have records in your [dbo].[UPSELL_DATA] table with values in the [AMRNO] column that don't exist in the [dbo].[AFFILIATE_MKTG_REF] table, [AMRNO] column. Try a query like this to find those that don't have matching records:

select   *
from     [dbo].[UPSELL_DATA] u
left join [dbo].[AFFILIATE_MKTG_REF] m
on       u.AMRNO = m.AMRNO
where    m.AMRNO is null