Can I refactor this query to use an index more efficiently?

Question

I have a members table with fields such as id, last name, first name, address, join date, etc.
I have a unique index defined on (last_name, join_date, id).
This query will use the index for a range scan, no sort required since the index will be in order for that range ('Smith'):
SELECT members.*
        FROM members
        WHERE last_name = 'Smith'
        ORDER BY joindate, idIs there any way I can get something like the following to use the index (with no sort) as well:
SELECT members.*
        FROM members
        WHERE last_name like 'S%'
        ORDER BY joindate, idI understand the difficulty is probably; even if it does a range scan on every last name 'S%' (assuming it can?), they're not necessarily in order. Case in point:
Last_Name:  JoinDate:
Smith          2/5/2010
Smuckers     1/10/2010An index range scan of 'S%' would return them in the above order, which is not ordered by joindate.
So is there any way I can refactor this (query or index) such that the index can be range scanned (using LIKE 'x%') and return rows in the correct order without performing a sort? Or is that simply not possible?

Answer 1

xaeryan wrote:
I have a members table with fields such as id, last name, first name, address, join date, etc.
I have a unique index defined on (last_name, join_date, id).
This query will use the index for a range scan, no sort required since the index will be in order for that range ('Smith'):
SELECT members.*
FROM members
WHERE last_name = 'Smith'
ORDER BY joindate, idIs there any way I can get something like the following to use the index (with no sort) as well:
SELECT members.*
FROM members
WHERE last_name like 'S%'
ORDER BY joindate, idI understand the difficulty is probably; even if it does a range scan on every last name 'S%' (assuming it can?), they're not necessarily in order. Case in point:
Last_Name:  JoinDate:
Smith          2/5/2010
Smuckers     1/10/2010An index range scan of 'S%' would return them in the above order, which is not ordered by joindate.
So is there any way I can refactor this (query or index) such that the index can be range scanned (using LIKE 'x%') and return rows in the correct order without performing a sort? Or is that simply not possible?Come on. Index column order does matter. "LIKE 'x%'" actually is full table scan. The db engine accesses contiguous index entries and then uses the ROWID values in the index to retrieve the table rows.