Tools: schema designer; scripts

I'm going to be working out several schemas which I'll need to
replicate. Are there any recommendable tools that easily allow you to
choose from existing scripts, update them, and run them, a la the MS
SQL Server client?

And to work on schema designs, a la Erwin (which I don't know well
but think does this and creates the CREATE TABLE scripts, etc.)?

(A quick scan of the archive didn't find any previous entries.)

Thanks!

Dennis

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