You can use the following Oracle PL/SQL statement to retrieve the primary key columns in an Oracle table.
SELECT cols.table_name, cols.column_name, cols.position, cons.status, cons.owner
FROM all_constraints cons, all_cons_columns cols
WHERE cons.constraint_type = 'P'
AND cons.constraint_name = cols.constraint_name
AND cons.owner = cols.owner
ORDER BY cols.table_name, cols.position;
If you knew the table name that you were looking for, you could modify the SQL as follows:
SELECT cols.table_name, cols.column_name, cols.position, cons.status,
cons.owner
FROM all_constraints cons, all_cons_columns cols
WHERE cols.table_name = 'TABLE_NAME'
AND cons.constraint_type = 'P'
AND cons.constraint_name = cols.constraint_name
AND cons.owner = cols.owner
ORDER BY cols.table_name, cols.position;
Make sure to type the table_name in uppercase, as Oracle stores all table names in uppercase.