Re: A DBMS implementation Question

Just slap another index on the age column. Every single RDBMS package that I can think of allows for multiple indexes.

"owen" <member25756_at_dbforums.com> wrote in message news:2587446.1046435126_at_dbforums.com...
>
> Some small rational dbms use B tree for indexing. I found a problem
in
> the condition that the key for the table is a multiple key. For
example
> , there is a table which is denoted as emp(no, age, name), and (no +
> age) is the key for indexing.In the B Tree, the values of "no" and
"age"
> are transfered to String and merge together, such as the key value
of
> (1, 20, "abc") is "00010020",and the the B Tree of the table is
> established by the sequence of the key.
> Now , I have a problem , if I want to query all the people
whose
> age are more than 20 , which is described as "select * from emp
> where age > 20", i can't use b tree for indexing, if i use ,
the
> number of records that i must scan may be very large, how to
sovle
> the problem.
> The problem can be expressed as "how to deal with scaning the
table
> using non-primary key or non-key field".
> thanks!!
>
> --
> Posted via http://dbforums.com
Received on Fri Feb 28 2003 - 21:13:05 CET