ORACLE 10G: drop tablespaces

 Dropping a Tablespace: Example

The following statement drops the tbs_01 tablespace and drops all referential integrity constraints that refer to primary and unique keys inside tbs_01:

DROP TABLESPACE tbs_01
    INCLUDING CONTENTS
        CASCADE CONSTRAINTS;

Deleting Operating System Files: Example
The following example drops the tbs_02 tablespace and deletes all associated operating system datafiles:

DROP TABLESPACE tbs_02
   INCLUDING CONTENTS AND DATAFILES;

Source:
http://www.stanford.edu/dept/itss/docs/oracle/10g/server.101/b10759/statements_9004.htm