Tool for convert SQL code to diagram

For MySQL can use sqlyog :

SQLyog MySQL GUI is the most powerful MySQL manager and admin tool, combining the features of MySQL Query Browser, Administrator, phpMyAdmin and other MySQL Front Ends and MySQL GUI tools in a single intuitive interface.

http://www.webyog.com/en/

using mysql Workbench do the following:

1- file -> new model

2- file -> import -> reverse engineer mysql create script

select ur mysql file script

and tick on place imported objects on a diagram

and press next and finish

Use MySQL WorkBench. It's perfect and absolutely compatible with MySQL, Oracle powered!

Check it out here: MySQL Workbench

ModelRight, http://www.modelright.com/ , is a good ERD application and is free for MySQL and ODBC connected databases. It reverse engineers from a DB, if you want to reverse engineer from SQL Script, you should check out Dezign for Databases, http://www.datanamic.com/