SQL Server delete trigger - row handle referred to a deleted row or a row marked for deletion

I have a delete trigger on a table which is used to delete entries from a table in an another database.

CREATE TRIGGER [dbo].[Trigger_Contracts_Delete] ON [dbo].[Contracts]
AFTER DELETE NOT FOR REPLICATION
AS
  IF @@ROWCOUNT = 0 RETURN

  DELETE seconddb.dbo.second_table 
  WHERE contractId IN (SELECT d.ContractID FROM deleted d)

When I delete a record using my application (legacy app nothing know about its internals) I get the error "Row handle referred to a deleted row or a row marked for deletion"

However when I modified this trigger to add an additional select statement (SELECT d.ContractID FROM deleted d) just before delete.. I do not get the error message. What could be the reason for it to work when select statement is added, is it that by issuing select on "deleted" I have locked the "deleted" table ? it be issuing a

CREATE TRIGGER [dbo].[Trigger_Contracts_Delete] ON [dbo].[Contracts]
AFTER DELETE NOT FOR REPLICATION
AS
   IF @@ROWCOUNT = 0 RETURN

   SELECT d.C开发者_如何学编程ontractID FROM deleted d;

   DELETE seconddb.dbo.second_table 
   WHERE contractId IN (SELECT d.ContractID FROM deleted d)

your table(s) are missing primary keys! add primary keys and the problem will go away.

If you alawys want to delete the records from the child table, why not set up cascading delte instead of a trigger?