How to delete/drop an user schema in Oracle

alter session set "_oracle_script"=true;

drop user <USER_SCHEMA> cascade;

Example:
drop user myUserSchema cascade;

How to limit the number of records returned in a SQL query

There is no a SQL standard to limit the number of records returned in a query, ie, each vendor implements this functionality in its own way.

Here's a summary on how to do this for some vendors:

DB2 -- select * from table fetch first 10 rows only 
Informix, InterBase/Firebird, SKIP  -- select first 10 * from table 
Microsoft SQL Server and Access -- select top 10 * from table 
MySQL, PostgreSQL, SQLite, HSQL/H2 -- select * from table limit 10 
Oracle -- select * from table where rownum <= 10

Oracle Note:

If the query has "group by" or "order by" rownum must be supplied:

Ex:

SELECT a, b, c
FROM
( SELECT a, b, c, ROWNUM rn
FROM
( SELECT a, b, c FROM RECORD 
WHERE AVAIL='Y"
ORDER BY DATE DESC
)
WHERE ROWNUM <= 25
)
WHERE rn >= 21;

References:

http://stackoverflow.com/questions/595123/is-there-an-ansi-sql-alternative-to-the-mysql-limit-keyword

http://www.macoratti.net/d250102.htm

http://www.dougboude.com/blog/1/2006/06/Equivalent-of-SQL-TOP-X-in-Oracle.cfm

http://www.dbforums.com/oracle/1214188-limit-clause-oracle-sql.html