Proper punctuation is a beautiful thing. Why no semi-colons at the end of your statements?

This worked for me:

--Create Test Table

CREATE TABLE [dbo].[Null_Table](

[CID] [int] NULL,

[MID] [int] NULL

) ON [PRIMARY];

GO -- execute the create table batch.

--Insert Sample Data --- note the semicolons!

insert into Null_Table(CID,MID)

valueS (123,456);

insert into Null_Table(CID,MID)

valueS (123,Null);

insert into Null_Table(CID,MID)

valueS (123,0);