Can You Add A Column To Wordpress Table? Will Upgrade Remove It?

Is this possible to add a column to wp_post? What will happen to it when it is upgraded? Is it possible to tell wordpress开发者_开发知识库 not to delete column if upgrade might remove it?

** Please do not post why I should use the other tables or make a new table. **

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I do not know off the top of my head whether it will get deleted when upgrading, but why would you want to do that? That's what the postmeta table is for.