In v9 of Oracle, there are all sorts of restrictions on what DDL you can perform on tables that are set for compression. In v10, some of the restrictions have been lifted - which of course makes this part of the database worth of some playing around.
For example, lets see what happens when we try to drop a column on a compressed partitioned table.
SQL> create table PARTAB
2 ( x number , y number)
3 partition by range ( x )
4 ( partition p1 values less than (100),
5 partition p2 values less than (200) );
Table created.
SQL> alter table PARTAB compress;
Table altered.
SQL> alter table partab drop column y;
alter table partab drop column y
*
ERROR at line 1:
ORA-39726: unsupported add/drop column operation on compressed tables
Now thats fair enough...and should be easy enough to solve. We'll just set the table to being uncompressed...
SQL> alter table PARTAB nocompress;
Table altered.
SQL> alter table partab drop column y;
alter table partab drop column y
*
ERROR at line 1:
ORA-39726: unsupported add/drop column operation on compressed tables
Ooopppsss....