Hi, guys. I need your advice here.

Instead of drawing the database schemas and then implement the database, I started off by implementing the database straight into MySQL scripts in a project. But now I need a diagramatic representation of the database for a presentation.

Are there any tools out there which can help generate the schema diagram automatically from a database?

I'm aware this post is a couple years old. But being linuxquestions.org the knowledge base it is. I thought I'd take the time to answer;

What you are trying to do is called "reverse engineering" There are several programs often referred to as "Entity Relationship(ER) Modeling". To name a few, you have; Xcase, mySQL Maestro, Case Studio (now toad), and from the dark side you got MS Visio (Visio doesn't fully support mySQL, you will encounter problems dealing with restrictions on data types availiable). Besides the afore mentioned there are many other ER Modeling Programs.

Another point to make is that these programs often use the myODBC driver to connect with mySQL.

Came across this while looking for software to reverse engineer the mythtv database because the schema details on the mythtv wiki are lacking IMO.
There is an ERD entry on wikipedia at http://en.wikipedia.org/wiki/Entity-relationship_model which references some more software.

There is a schema browser in TOra (supposed to have mysql support), but a quick install under ubuntu doesn't give me access.
A search for "tora mysql" returns a .rpm plugin, but I get a connection refused message from sourceforge if I try downloading it.

http://schemaspy.sourceforge.net/

Not stricly an ER diagram, but it will produce some very useful digrams of your database structure. If you are using MySQL, then you need to name the columns appropraitly so it can guess the relationships.