CREATE TABLE dbo.SampleTable
  (
   C1 INT NOT NULL,
   C2 INT NOT NULL )

ALTER TABLE dbo.SampleTable ADD CONSTRAINT IDX_SampleTable PRIMARY KEY CLUSTERED (C1, C2)

ALTER TABLE dbo.SampleTable ADD CONSTRAINT IDX_SampleTable PRIMARY KEY NONCLUSTERED (C1, C2)
CREATE CLUSTERED INDEX IDX_SampleTable2 ON dbo.SampleTable (C1 ,C2)    -- Can not create Same Name With above Constraint Name