Check out example codes for "oracle search columns in schema". It will help you in understanding the concepts better.

Code Example 1

select t.owner as schema_name,
       t.table_name , col.column_name
from sys.all_tab_columns col
inner join sys.all_tables t on col.owner = t.owner 
                              and col.table_name = t.table_name
where col.column_name = ''
and col.owner not in ('')
order by col.owner, 

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