create or replace procedure dbname is
v_dbname varchar2(30);

begin
select name into v_dbname from v$database;
dbms_output.put_line('db name is: '||v_dbname);
end;


相关说明：
1.必须由dba执行，否则出错。
2.执行前须 set serveroutput on
3.依此方式执行：
exec dbname



附录：同事写的一个PL/SQL，可以试一下。注意：不要用sys用户执行。

create or replace procedure test is
v_tname tab.tname%type;
v_count number;
cursor tab_cursor is
select tname from tab;
begin
open tab_cursor;
loop
fetch tab_cursor into v_tname;
execute immediate 'select count(*) from '||v_tname into v_count ;
dbms_output.put_line(v_tname||' '||to_char(v_count));
exit when tab_cursor%notfound;
end loop;
close tab_cursor;
end;

执行方法：
set serveroutput on
exec test

我的那份在这儿，可是却不能执行。
create or replace procedure tabcount is
v_tname varchar2(30);
v_count number;
v_size number;

begin
select count(*) into v_size from tab;
loop
select tname into v_tname from tab where rownum=v_size;
execute immediate 'select count(*) from '||v_tname into v_count;
dbms_output.put_line(v_tname||' '||to_char(v_count));
v_size:=v_size-1;
exit when v_size=0;
end loop;
end;

ERROR at line 1:
ORA-01403: no data found
ORA-06512: at "SCOTT.TABCOUNT", line 8
ORA-06512: at line 1

=========
added by 20050804.
今天学了游标，偶终于也写了一个不会出错的了。

    create or replace procedure tabcount is
    v_tname varchar2(30);
    cursor sor is select tname from tab;
    v_count number;
    begin
    open sor;
    dbms_output.enable(200000);
    v_count:=0;
    loop
    fetch sor into v_tname;
    dbms_output.put_line('tname is '||v_tname);
    v_count:=v_count+1;
    exit when sor%NOTFOUND;
    end loop;
    dbms_output.put_line('counts of tname is '||to_char(v_count));
    close sor;
    end;

嘿嘿，太好了。