The problem is that I don't understand your answer.
(maybe because English is not my native language and also because
I'm new to databases)
I have generated DDLs from Sybase Central but I don't have PowerDesigner
that can do a "reverse engineering" from the DDLs and create a nice DB Schema.
So what do you mean with "Use the script tool for your database engine"?
I'm assuming that you mean that you have a script of DDL including statements like CREATE TABLE. If that is the case, then the script is actually intended to be played via ISQL.EXE or whatever tool you'd normally use to issue a SELECT, INSERT, DELETE or similar statement. You shouldn't need any special tools to execute DDL.
Maybe I understand your question better (then again, maybe I don't).
Are you trying to create an ERD (Entity-Relationship Diagram) from an existing database? In other words, do you already have the database (not a script to build a database), and you want a picture that shows the schema of that database graphically?
I have a database (Sybase) and from that I have used Sybase Central
to generate the DDLs that builds up the dB.
And just as you say, it would be good if there was some tool that could
show a "picture" of it (ERD).
I know that PowerDesigner can do this but are there any other tools that
can create an ERD from DDLs?
There are many tools that can create an ERD from a database.
PowerDesigner is a good choice, especially for a Sybase database (for obvious reasons). ErWin is quite expensive, but it is certainly the "tool of choice" for data modeling professionals. Microsoft offers a variety of tools that can produce ERDs.