A DBMS implementation Question
Date: Fri, 28 Feb 2003 12:25:26 +0000
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.comReceived on Fri Feb 28 2003 - 13:25:26 CET