SELECT rows with unique values in two columns

Question

I have a table like this:

id          col1 col2        
----------- ---- ----------- 
1           A    5
2           A    6
3           B    5
4           B          


        

Answer 1

try the following using cursor:

create table #final (id int, col1 varchar(10), col2 int)

declare @id int, @col1 varchar(10), @col2 int
declare cur cursor for select id, col1, col2 from #t order by newid()

open cur
fetch next from cur into @id, @col1, @col2
while @@FETCH_STATUS = 0
begin
    if (@col1 in (select col1 from #final) or @col2 in (select col2 from #final))
    begin
        fetch next from cur into @id, @col1, @col2
        continue
    end
    insert into #final
    select id, @col1, @col2 from #t where col1 = @col1 and col2 = @col2 and id = @id
    fetch next from cur into @id, @col1, @col2
end

close cur
deallocate cur

select * from #final order by id

drop table #final

Result:

Answer 2

Try this query:

SELECT  id, col1, col2
FROM ( SELECT    * ,
       RANK() OVER ( PARTITION BY col2 ORDER BY col2 ) Row#
       FROM      #t
     ) x
WHERE   x.Row# = 1

Answer 3

This is not an easy one to solve through straight SQL. I figured I'd give it a crack using a recursive CTE. This spits out all possible combinations, but... in one field called "path" here. Perhaps it will present a way forward using straight tsql.

With recCTE AS
(
    SELECT 
      col1, 
      col2, 
      0 as depth, 
      CAST(col1 + '|' + CAST(col2 AS varchar(10)) AS VARCHAR(30)) as path 
    FROM t

    UNION ALL

    SELECT       
      t1.col1, 
      t1.col2, 
      rec.depth + 1, 
      CAST(rec.path + '>' + t1.col1 + '|' + cast(t1.col2 as varchar(10)) as varchar(30))
    FROM t t1
        INNER JOIN recCTE rec
        ON rec.path NOT LIKE '%|' + CAST(t1.col2 as varchar(10)) + '%'
           AND rec.path NOT LIKE '%' + CAST(t1.col2 as varchar(10)) + '|%'
    WHERE depth + 1 <= 3 

)
SELECT * 
FROM recCTE 
WHERE depth = 2

Answer 4

SELECT  id, col1, col2
FROM    ( SELECT    * ,
                    ROW_NUMBER() OVER ( PARTITION BY col2 ORDER BY col2 ) Row#
          FROM      #t
        ) x
WHERE   x.Row# = 1