Problem of RDBMS's implementation

I am in the study of database techology, my class design is to implement a small rational db, I have read some papers, and I decide to use b tree for indexing, and I want to express key by string, which is the means I described in the before article, but the problem I expressed has anonyed me until now , so welcome to give some advise to me?i am waiting for you , thanks

--
Posted via http://dbforums.com