select upper('testmyname') from dual;  --转换为大写 
select lower('testmyname') from dual; --转换为小写
select upper(substr('testmyname'),5) from dual; --截取myname，并转换为大写
selec instr('testmyname','or') from dual; --查找字符'or'，返回0
select tim('  hi  ) from dual; --返回hi
select rpad('smith',10,'月') as reft_star_smith,lpad('smith',10,'月') as ri
 ght_star_smith from dual;          --左右俩侧填充字符