what made the difference?

Hi all
I have the table with the following data (sample):

81 123 1
81 123 2
81 123 3
....

81 124 1
81 124 2
81 124 3
81 124 4
....

So, first column is always the same, second column is sequence number and third column is sub-sequence number. There are multiple sub-sequences for the same sequence(always).

We had an index as (col1,col2,col3) and performance was poor. After we changed the same index to (col2,col3,col1) performance problem disappeared (actually it became much faster).

My question is: Why changing column order of an index made such difference. What is it about changing the order of index columns that make a particular index perform better?

Thanks,
Eugene Received on Fri May 06 2005 - 12:44:29 CDT