buppcpp wrote:

> Everytime I issue a query that has 3 or more table in it, and each
> table is joined on index fields with high selectivity (mainly
> primary key fields), the first table in the plan ALWAYS does a table
> scan ('NATURAL' in PLAN lingo).

Lets think a minute about what you're asking for and how the database
can resolve your query.

select a.name, b.department, c.company
from employees a
join departments b on a.DeptID = b.DeptID
join companies c on b.CompanyID = c.CompanyID

You've asked for the names of all employees with the names of their
departments and companies. The fastest way to get all the employee
names is to read the employee table from front to back - a natural scan.
Once you have an employee record, you can lookup the department by its
key value, DeptID. Once you have the department record, you can look up
the company by its key value, CompanyID. But when you start, you don't
have any key to lookup in the employee table.

If you add a where clause that restricts the employee records you want
to see based on the value of an indexed field in that table, then the
database can and will use an index on that table.

Regards,


Ann