How to sql-recursive statements work?

Question

I am trying to understand sql recursive statements, but it is really hard for me. For example:

Thats an exampe I am trying to understand and to write down the output.

Can sb pls explain me how this works, step by step?

greetings and thx in advance

maya

Answer 1

Also, see here - http://www.postgresql.org/docs/8.4/static/queries-with.html, where the steps of the recursive query evaluation are described.

Answer 2

The UNION ALL portion gets recursed until it returns no more records. I don't know if you can have multiple UNION ALL portions.