getting column names

Hi

Can somebody please tell me if the below is possible ?

I may not see the forest from the trees

Thanks
Armand

levregdb=# select * from foo1;
audit_id | table_name
----------+------------
6012 | foo2
6013 | foo2
6014 | foo2

select * from foo2;

levregdb=# select * from foo2;
foo2_add_by | foo2_add_date
-------------+---------------
(0 rows)

levregdb=# \d foo2;
Table "csiprev.foo2"
Column | Type | Modifiers
---------------+---------------+-----------
foo2_add_by | character(10) |
foo2_add_date | character(10) |

My intention is to have an output like

6012 | foo2|foo2_add_by|foo2_add_date
6013 | foo2|foo2_add_by|foo2_add_date
6014 | foo2|foo2_add_by|foo2_add_date

select a.audit_id, a.table_name, b[1],b[2]
from
foo1 a,
(select
array(
select
column_name::text from
information_schema.columns
where
table_name='foo2'
and
(
column_name like '%add_by%'
or
column_name like '%add_date%'
)) b) as foo
;

audit_id | table_name | b | b
----------+------------+-------------+---------------
6012 | foo2 | foo2_add_by | foo2_add_date
6013 | foo2 | foo2_add_by | foo2_add_date
6014 | foo2 | foo2_add_by | foo2_add_date

But if I join back to foo1 like below I get

select a.audit_id, a.table_name, b[1],b[2]
from
foo1 a,
(select
array(
select
column_name::text from
information_schema.columns
where
table_name=a.table_name
and
(
column_name like '%add_by%'
or
column_name like '%add_date%'
)) b) as foo
;

ERROR: invalid reference to FROM-clause entry for table "a"
LINE 10: table_name=a.table_name
^
HINT: There is an entry for table "a", but it cannot be referenced from this part of the query.

Any idea what am I doing wrong ?
Can I do it ?

Thanks
Armand

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