oracle 记录,嵌套表,集合
1.exists 检查集合中是否存在某个元素,collection.exists(index)
2.count 返回集合中元素的个数 collection.count
3.limit 返回varray中最大的条目数,关联数组和嵌套表返回空
4.first 返回集合的第一个元素
5.last 返回集合的最后一个元素
6.next 返回集合中的下一个元素,如果不存在返回空 collection.next
7.prior 返回集合中的上一个元素,如果不存在返回空
8.extend 扩展集合中元素的个数,不用于关联数组,和未被初始化的集合
collection.extend,collection.extend(n),collection.extend(n,i)
9.trim 从集合的结尾处删除元素
collection.trim(),collection.trim(n)
10.delete 从集合中删除元素 collection.delete,collection.delete(n),collection.delete(m,n)[i][/i]

---使用数组将查询的记录存放到嵌套表中declare  type deptrecord is record  (     deptno dept.deptno%type,     dname dept.dname%type,     loc dept.loc%type  );  type number_array is table of deptrecord;  number_collection number_array:=number_array();begin  number_collection.extend(5);  dbms_output.put_line('number_collection的数量：'||number_collection.count);  select * bulk collect into number_collection from dept;  dbms_output.put_line('number_collection的数量：'||number_collection.count);  for currow in number_collection.first .. number_collection.last loop    dbms_output.put_line(number_collection(currow).deptno);  end loop;end;---使用数组将查询的记录存放到嵌套表中declare  type deptrecord is record(    deptno dept.deptno%type,    dname  dept.dname%type,    loc    dept.loc%type);  type number_array is table of deptrecord;  number_collection number_array := number_array();  i                 number := 0;  curroww           number;begin  for currow in (select * from dept) loop    i := i + 1;    number_collection.extend;    number_collection(i).deptno := currow.deptno;    number_collection(i).dname := currow.dname;    number_collection(i).loc := currow.loc;  end loop;  for i in 1 .. number_collection.count loop    dbms_output.put_line('');    dbms_output.put_line('循环方式一');    dbms_output.put_line('deptno:=' || number_collection(i).deptno);    dbms_output.put_line('dname:=' || number_collection(i).dname);    dbms_output.put_line('loc:=' || number_collection(i).loc);  end loop;  for i in number_collection.first .. number_collection.last loop    dbms_output.put_line('');    dbms_output.put_line('循环方式二');    dbms_output.put_line('deptno:=' || number_collection(i).deptno);    dbms_output.put_line('dname:=' || number_collection(i).dname);    dbms_output.put_line('loc:=' || number_collection(i).loc);  end loop;  curroww := number_collection.first;  loop    exit when curroww is null;    dbms_output.put_line('');    dbms_output.put_line('循环方式三');    dbms_output.put_line('deptno:=' || number_collection(i).deptno);    dbms_output.put_line('dname:=' || number_collection(i).dname);    dbms_output.put_line('loc:=' || number_collection(i).loc);    curroww := number_collection.next(curroww);  end loop;end;