Easiest way to eliminate NULLs in SELECT DISTINCT?

Question

I am working on a query that is fairly similar the following:

CREATE TABLE #test (a char(1), b char(1))

INSERT INTO #test(a,b) VALUES 
(\'A\',NULL),
(\'A\',         


        

Answer 1

;WITH CTE
    AS
    (
    SELECT DISTINCT * FROM #test
    )
    SELECT a,b
    FROM CTE        
    ORDER BY CASE WHEN b IS NULL THEN 9999 ELSE b END ; 

Answer 2

I'll just put here a mix of two answers that solved my issue, because my View was more complex

    --IdCompe int,
    --Nome varchar(30),
    --IdVanBanco int,
    --IdVan int
    --FlagAtivo bit,
    --FlagPrincipal bit

    select IdCompe
           , Nome
           , max(IdVanBanco)
           , max(IdVan)
           , CAST(MAX(CAST(FlagAtivo as INT)) AS BIT) FlagAtivo
           , CAST(MAX(CAST(FlagPrincipal as INT)) AS BIT) FlagPrincipal
    from VwVanBanco
           where IdVan = {IdVan} or IdVan is null
           group by IdCompe, Nome order by IdCompe asc

Thanks to mosty mostacho and kenwarner

Answer 3

Well, I don't particularly like this solution, but it seems the most appropriate to me. Note that your description of what you want sounds exactly like what you get with a LEFT JOIN, so:

SELECT DISTINCT a.a, b.b
FROM #test a
    LEFT JOIN #test b ON a.a = b.a
        AND b.b IS NOT NULL

Answer 4

SELECT a,b FROM #test t where b is not null
union
SELECT a,b FROM #test t where b is null
and not exists(select 1 from #test where a=t.a and b is not null)

Result:

a    b
---- ----
A    B
B    NULL

Answer 5

This is a really weird requirement. I wonder how you need it.

SELECT DISTINCT a, b
FROM   test t
WHERE  NOT ( b IS  NULL
          AND EXISTS 
              ( SELECT * 
                FROM test ta 
                WHERE ta.a = t.a 
                  AND ta.b IS NOT NULL
               ) 
             )
  AND  NOT ( a IS  NULL
          AND EXISTS 
              ( SELECT * 
                FROM test tb 
                WHERE tb.b = t.b 
                  AND tb.a IS NOT NULL
               ) 
             )

Answer 6

SELECT DISTINCT t.a, t.b
FROM   #test t
WHERE  b IS NOT NULL
OR     NOT EXISTS (SELECT 1 FROM #test u WHERE t.a = u.a AND u.b IS NOT NULL)
ORDER BY t.a, t.b