Is there a good way to link tables and sequences? I'm pretty sure you can't do this like you can with foreign keys but I'd like to document at the database level (even if it's just as a bit of free text somewhere) these relationships.

Is there some way of adding comments to tables or something like that?  I've noticed comments in the sql used to create things are often preserved but not sure how you edit these without recreating the whole object or how you view them without dumping ddl.

I'm interested in doing this in sqlserver and oracle.  I'm primarily doing edits from the command line/scripts but often look at the databases using SSMS and Sql developer.

The reason I'm interested in this is to let other developers know how to use the database - both future devs + the ones I'm currently working with.  We've got 3 applications using the same db and unfortunately its missing primary key and foreign key constraints in a lot of areas, whilst putting those in will go a long way to making it easier to understand, this would also help a lot aswell. 

One hacky way I can think of doing it is adding an extra column to each table with the sequence name but I dont really like that - think its a bit misleading.
Easy in Oracle:

comment on table mytable is 'This is a table comment';

comment on column mytable.mycolumn is 'This is a column comment';


You can then view the comments using the USER_TAB_COMMENTS and USER_COL_COMMENTS data dictionary views.

This answer covers it for SQL Server.