SELECT *
FROM
(
SELECT ROW_NUMBER() OVER (PARTITION BY a.[BLS_io],a.[iCom]  ORDER BY (SELECT 1)) AS rn,
,a.[BLS_io] iFMB

,imiters_io = b1.[miters_io]
,a.[iCom] cFMB

,cmiters_io = b2.[miters_io]
,a.[FoV]

FROM [BLS].[IO2012].[ACxC_1993] a
left join [BLS].[IO2012].[io_concord_new] b1
on a.[BLS_io] = b1.[fmb_io] 
left join ,[BLS].[IO2012].[io_concord_new] b2
on a.[iCom] = b2.[fmb_io]
WHERE b1.[fmb_io] is not null
or  b2.[fmb_io] is not null
)t
WHERE Rn=1