dynamic name of table in select

Hi to all,
I need help about the following issue:
in my db I've three table which have the same column (there are some reasons
for that) I'd like to perform a select statement like that: select my_column
from xxx_table .
Where xxx could be choosen from another table result.
for example :

select my_column from (select name_table from catalog where condition1)

now the internal select has to return the name of the table which is linked
to the condition1 (let me say condition1_table) so after the inner select
has been perfomed, I should have

select my_column from condition1_table

Is it possible ?

Second question: is there a system variable where the name of the db is
stored ? how can I recall it?

Thanks in advance and best regards

Giu
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