To get the column names, data types, and nullables of tables in the schema owned by MASTER_USER

select    t.table_name,   t.column_name,   t.data_type,   t.NULLABLE,   (SELECT col.column_name    FROM all_constraints cons, all_cons_columns col    WHERE col.table_name = t.table_name                       AND cons.constraint_type = 'P'                       AND cons.constraint_name = col.constraint_name                       AND cons.owner = col.owner and cons.owner = 'MASTER_USER'   )  Primary_Key_Column