There is no one command to do this, you could write a PL procedure to do it, or generate the SQL statements from USER_TABLES. Alternately some IDE's provide an easier way.
You have two options:
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1) Create a script
set lines 200;
set pages 10000;
spool c:\DROP_TABLES.txt;
select 'DROP TABLE '||table_name||';'
from all_tables
where owner = 'SCOTT';
-- change the SCOTT to the owner of the tables you need to drop.
spool off;
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@c:\DROP_TABLES.txt; -- to run the script that we created.
-- repeat this step tell u drop all the tables.
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2) From the Enterprise Manager , Drop the owner Schema.
DECLARE
table_name VARCHAR2(30);
CURSOR usertables IS SELECT * FROM user_tables WHERE table_name NOT LIKE 'BIN$%';
BEGIN
FOR next_row IN usertables
LOOP
EXECUTE IMMEDIATE 'drop table ' || next_row.table_name || ' cascade constraints';
END LOOP;
END;
save it as a .sql file and run it from oracle sql plus using this command@path\filename.SQL / will remove all tables from USER_TABLES (where all the user tables are created ) in the current schema pointed to SQL PLUS