Question

I had the below code, but it is showing all records due to the UNION:

'WITH x AS
( 
  SELECT m, ' + @columnlist + ', rn = ROW_NUMBER() OVER (PARTITION BY ClientNric ORDER BY m DESC) 
  FROM  
  (   
    SELECT m = ''' + @table1 + ''', * FROM ' + @table1 + '
    UNION ALL  
    SELECT m = ''' + @table2 + ''', * FROM ' + @table2 + '
  ) AS y 
) 
SELECT ' + @columnlist + ', DataState = m 
  FROM x  
  WHERE rn = 1;'

exec(@sql)

I need the results as follows:

table1 
ID   Name 
1    TestA 
2    TestB     
3    TestC 
4    TestD 

table2 
ID   Name 
1    TestE 
2    TestF     
3    TestG 
4    TestD 

Results: 
Name     DataState 
TestA    table1 
TestB    table1 
TestC    table1 
TestD    table2 

Can advise how to achieve the results?
Thanks.

Answer 1

A left join should do the job, I think:

SELECT
  t1.Name,
  DataState = COALESCE(t2.DataState, 'table1')
FROM table1 t1
  LEFT JOIN (
    SELECT
      Name,
      DataState = 'table2'
    FROM table2
  ) t2 ON t1.Name = t2.Name

Or maybe the join should be on the ID column, I’m not sure. In any event, this should at least give you the idea.