how to do this join ?

Hello there

I have another SQL question. Please see the example :

select *,
(select a_typ from auftrag where a_nr=z_a_nr) as typ,
(select a_t_definition_d from auftrags_typ where a_t_code=typ) as text
from zylinder

I have three tables that I need data from. I'd like to use the <as typ> to
temporary store the kind of auftrag and then use it to get the
definition (clear text) from another table.

The query returns that typ is not known .

How can I do it ?

Thanks ... jr
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