Can I have one table be an "alias", or "symlink", to another? I have two tables with the same structure, A and B. A certain application is written so that it always writes the same data to both tables.

After a discussion with a colleague about the potential to save drive space, I'm wondering if mysql or postgresql has the ability to create on table as an "alias", or "symlink", of another.

I want the behaviour to be very similar to that of a soft file symlink; where reading from either the symlink itself or it's target will yield the same output, and writing to either will update the target.
As far as I know, a new Postgresql lets you have INSTEAD OF triggers on views. So having one table, one view as SELECT * FROM table1, and INSTEAD OF trigger for insert, update, delete should work for you. This approach is not gonna work in Mysql though