parent_id int not null	-- код изделия 
child_id int not null 	-- код изделия, входящего в состав parent_id 
qnt float not null	-- кол-во изделий child_id в составе изделия parent_id

select child_id, qnt from t where parent_id = @a

select child_id, qnt from t where parent_id = @b

if exists ( select *
                from ( select child_id, qnt from t where parent_id = @a ) as a
                       full outer join
                       ( select child_id, qnt from t where parent_id = @b ) as b
                       on a.child_id = b.child_id and a.qnt = b. qnt
                where a.child_id is null or b.child_id is null
           )
print 'Различаются!'

select * from a
union
select * from b

IF EXISTS
(
 SELECT * FROM t WHERE parent_id=@a AND NOT EXISTS(SELECT * FROM t t2 WHERE t2.parent_id=@b AND t2.child_id=t.child_id AND t2.qnt=t.qnt)
 UNION ALL
 SELECT * FROM t WHERE parent_id=@b AND NOT EXISTS(SELECT * FROM t t2 WHERE t2.parent_id=@a AND t2.child_id=t.child_id AND t2.qnt=t.qnt)
)
PRINT 'Различаются';

IF EXISTS
(
 SELECT *
 FROM t
 WHERE t.parent_id IN(@a,@b)
   AND NOT EXISTS
           (
            SELECT *
            FROM t t2
            WHERE t2.parent_id IN(@a,@b)
              AND t2.parent_id<>t.parent_id
              AND t2.child_id=t.child_id
              AND t2.qnt=t.qnt
            )
)
PRINT 'Различаются';