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

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