how to know databases space information?

[yindu]

hello,sir
        i had created a database for user on my server,i want to know how much space 
of the database have been used,and how much left.
in sql server i do it with some stored precedures,
but i did not found same stored precedures in mysql,please tell me what to do and why 
to do like that.thank you!
                                yin du