Would be nice to have a section on 'Tables'

I can see that there's a section on commands, but to follow through with the flow of a _tutorial_ I think it would be super nice to have a section that described the following...:

- The general concepts of a table (columns, rows, etc.)
- How the above applies to Postgres.
- How to _add_ and _delete_ table
- How to _add_, _delete_, _update_ columns
- What column and table constraints are

... in a way that allowed users to have a 'complete' table by the end of that section (and the two sections (on adding a user + database) before it).