游标嵌套使用,create or replace procedure MULTIPLE_CURSORS_PROC is
v_owner varchar2(40);
v_table_name varchar2(40);
v_column_name varchar2(100);

/* First cursor */
cursor get_tables is
select distinct tbl.owner, tbl.table_name
from all_tables tbl
where tbl.owner = 'SYSTEM';

/* Second cursor */
cursor get_columns is
select distinct col.column_name
from all_tab_columns col
where col.owner = v_owner
and col.table_name = v_table_name;

begin

-- Open first cursor
open get_tables;
loop
fetch get_tables into v_owner, v_table_name;

open get_columns;
loop
fetch get_columns into v_column_name;

end loop;
close get_columns;

end loop;
close get_tables;

EXCEPTION
WHEN OTHERS THEN
raise_application_error(-20001,'An error was encountered - '||SQLCODE||' -ERROR- '||SQLERRM);