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This is not producing results for T2.f2 rows with NULL value. I assumed that would have resulted in something like T1.f1 like '%' .

Any ideas?

I am not completely sure of what you're attempting;
however, to get around the specific issue you have, try COALESCE :

SELECT * 
  FROM T1 
       JOIN T2 
       ON T1.f1 LIKE CONCAT( COALESCE( T2.f2, '' ), '%' );
                Thanks, seems the original issue was not with NULLs (I saw empty values in the f2 columns). The rogue T2.f2 rows had only spaces in them. So the T1.f1 values were not matching with them. I used a TRIM(T2.f2), much like coalesce here. As newbie I do not have reputation to vote up, but my sincere thanks for the helping hand.
– nom-mon-ir
                Jun 25, 2011 at 2:01
                In Oracle '' and NULL are the same thing. So COALESCE( T2.f2, '' ) is exactly the same as T2.f2
– bart
                Jun 25, 2011 at 17:44
                Should be coalesce(concat(T2.f2, '%'), '%') or coalesce(T2.f2||'%', '%') to get a '%' in the face of null values for T2.f2.
– Shannon Severance
                Jun 26, 2011 at 9:15
        
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