Query output with indentation

Question

I have table System

component | subcomponent  (foreign key with subsystem table)
----------+-------------
cpu       |  1
monitor   |
lcd       |
keybord   |
mouse            


        

Answer 1

It's possible using e.g. a left join and some of the string formatting functions:

select ... as parent, '  -- ' || coalesce(..., '') as child
from ... left join ... on ...

You could also union things instead, etc. to get exactly what you requested.

BUT you really ought to leave that up to the view, as already suggested.