Question

I have a table with 21 columns (all integers) id, c1 , c2 … c20 and what to fetch ids for rows that have the same values in the columns …

so row 1 will match row 10 if row 1 c1 = row 10 c1 and row 1 c2 = row 10 c2 … and so on.

This is what the query looks like:

 select r1.id, r2.id 
 from tbl r1, tbl r2  
 where 1=1 and r1.c1=r2.c1 and r1.c2=r2.c2 and 
         ..... r1.c20=r2.c20 and not r1.id=r2.id 

I am currently using self join, but this is way too slow (20 secs for 10000 rows).
I have setup indexes on the columns (?)
I have ~ 1 million rows
Thanks

Answer 1

Have you tried a single index on all 20 columns?