使用SQL Server 2008 R2区分两列

Question

I have a select query as shown below:

 select cola,colb,colc,cold,cole,colf,colg,colh,coli,colj,colk
 from test
 where cola in (select colb from test);

How can I get only distinct cola and colb from different columns?

My try:

 select Distinct cola,colb,colc,cold,cole,colf,colg,colh,coli,colj,colk
 from test
 where cola in (select distinct colb from test);

Answer 1

You could use ROW_NUMBER with a CTE :

WITH CTE AS
(
 select cola,colb,colc,cold,cole,colf,colg,colh,coli,colj,colk,
        rn = ROW_NUMBER() OVER (PARTITION BY cola, colb ORDER BY cola)
 from test
 where cola in (select colb from test)
)
SELECT  cola,colb,colc,cold,cole,colf,colg,colh,coli,colj,colk
FROM CTE
WHERE rn = 1

This selects arbitrary rows for every cola, colb combination. If you want to fine-tune it change ORDER BY cola to something more meaningful.