oracle基础学习

--解锁用户，需要使用dba权限
conn sys/1234 as dba;

alert user scott account unlock;
/

--initcap方法，实现字符串首字符大写，其余字符小写，受空格，逗号等非字母符号限制         
select initcap(‘hello word,da jia hao!‘) Hello from dual;


--平均工资大于2000的分组
select avg_sal,deptno from 
    (select avg(sal) avg_sal,deptno from emp group by deptno) 
where avg_sal >2000;

having语句用法：
select avg(sal),deptno from emp group by deptno having avg(sal) > 2000;
/

--求部门中哪些人的薪水最高
select ename,sal from emp e join (select max(sal) max_sal,deptno from emp group by deptno) t on (e.deptno = t.deptno and e.sal = t.max_sal)
/
--求部门平均薪水的等级
select deptno,avg_sal,grade from salgrade s join (select avg(sal) avg_sal,deptno from emp group by deptno) t on (t.avg_sal between s.losal and hisal)
/
--求部门平均的薪水等级
select avg(t.grade) avg_grade,t.deptno from (select ename,deptno,grade from emp e join salgrade s on (e.sal between s.losal and s.hisal)) t group by t.deptno
/
--雇员中哪些人是经理人
select ename from emp where empno in (select distinct mgr from emp)
/
--不用函数求薪水的最高值
select distinct ename,sal from emp where sal not in (select distinct e1.sal from emp e1 join emp e2 on (e1.sal <e2.sal))
/
select t.ename,t.sal from (select ename,sal from emp order by sal desc) t where rownum<2（当最大薪水有多值时不对）
/
--求平均薪水最高的部门的部门编号
select deptno,avg_sal from 
(select avg(sal) avg_sal,deptno from emp group by deptno) 
where avg_sal = 
(select max(avg_sal) from (select avg(sal) avg_sal,deptno from emp group by deptno)
)

等同于：
select deptno,avg_sal from
(select avg(sal) avg_sal,deptno from emp group by deptno)
where avg_sal = 
(select max(avg(sal)) from emp group by deptno)
/
--求平均薪水最高的部门名称
select dname from dept where deptno = 
(
    select deptno from 
        ( select deptno,avg(sal) avg_sal from emp group by deptno ) 
    where avg_sal =
        ( select max(avg_sal) from 
            (select avg(sal) avg_sal,deptno from emp group by deptno) 
        )
)
/
--求平均薪水的等级最低的部门的部门名称
select t.deptno,t.dname from dept t where t.deptno = 
(
    select deptno from 
    (
        select deptno,grade,avg_sal from 
            (select avg(sal) avg_sal,deptno from emp group by deptno)     
            join salgrade s on (avg_sal between s.losal and s.hisal)
        where grade = 
            (
                select min(grade) from 
                (
                    select deptno,grade,avg_sal from 
                        (select avg(sal) avg_sal,deptno from emp group by deptno)     
                    join salgrade s on (avg_sal between s.losal and s.hisal)
                )
            )
    )    
)
等同于：
select t.deptno,dname,avg_sal,grade from
(
    select deptno,avg_sal,grade from
        (select avg(sal) avg_sal,deptno from emp group by deptno) t1
    join salgrade s on (t1.avg_sal between s.losal and s.hisal)
) t
join dept d on (t.deptno = d.deptno)
where t.grade = 
    (
        select min(grade) from 
        (
            select deptno,avg_sal,grade from
                (select avg(sal) avg_sal,deptno from emp group by deptno) t1
            join salgrade s on (t1.avg_sal between s.losal and s.hisal)
        )    
    )


/
--求平均等级最低的部门名称
select t.dname from dept t where t.deptno = 
( 
    select deptno from 
        ( select deptno,avg(grade) avg_grade from
            ( select e.deptno,s.grade from emp e join salgrade s on (e.sal between s.losal and s.hisal)
            ) 
        group by deptno
        ) 
    where avg_grade = 
        ( select min(avg_grade) from 
            (select deptno,avg(grade) avg_grade from 
                (select e.deptno,s.grade from emp e join salgrade s on (e.sal between s.losal and s.hisal) 
                ) 
            group by deptno 
            ) 
        ) 
)
/
--创建视图，首先赋予权限
conn sys/1234 as sysdba; sys不校验密码，任意密码即可。
grant create table,create view to scott;

create view v_dept_avg_sal_info as
select deptno,grade,avg_sal from
(select deptno,avg(sal) avg_sal from emp group by deptno) t
join salgrade s on (t.avg_sal between s.losal and s.hisal);

因此，求平均等级最低的部门名称可以用一下语句替换：
select t.deptno,d.dname,avg_sal,grade from
v_dept_avg_sal_info t 
join dept d on (t.deptno = d.deptno)
where t.grade = (select min(grade) from v_dept_avg_sal_info);

/

--求部门经理人中平均薪水最低的部门名称(经理人指empno存在于mgr中的员工)

select dname, t.deptno, avg_sal
  from (select deptno, avg(sal) avg_sal
          from emp
         where empno in (select distinct mgr from emp where mgr is not null)
         group by deptno) t
  join dept d
    on (d.deptno = t.deptno)
 where t.avg_sal =
       (select min(avg_sal)
          from (select deptno, avg(sal) avg_sal
                  from emp
                 where empno in
                       (select distinct mgr from emp where mgr is not null)
                 group by deptno))

创建视图v_mgr_sal_info，如下： 
create view v_mgr_sal_info as
select deptno, avg(sal) avg_sal
  from emp
 where empno in (select distinct mgr from emp where mgr is not null)
 group by deptno;

select dname, t.deptno, avg_sal
  from v_mgr_sal_info t
  join dept d
    on (d.deptno = t.deptno)
 where t.avg_sal = (select min(avg_sal) from v_mgr_sal_info);

/

--求比普通员工的最高薪水还高的经理人名称：

select ename
  from emp
 where empno in (select distinct mgr from emp where mgr is not null)
   and sal >
       (select max(sal)
          from emp
         where empno not in
               (select distinct mgr from emp where mgr is not null))
/

--删除用户
drop user mc cascade;
--备份用户 
backup scott
exp
--创建用户
create user mc identified by 1234 default tablespace quota 10M on users;
--赋予权限
grant create session,create table,create view to mc;
--导入数据
imp


--快速备份表，即创建一个一样的表
create table dept1 as select * from dept;


--求薪水值最高的前五名雇员；
select ename,sal from 
    (select ename,sal from emp order by sal desc ) 
where rownum<6;

/
--求薪水值第六名到第十名的雇员；
select ename,sal from
    (select ename,sal,rownum r from
        (select ename ,sal from emp order by sal desc)
    )
where r>5 and r <11;

/

/*
*
* 有3个表S,C,SC
* S(SNO,SNAME)代表（学号，姓名）；
* C（CNO，CNAME，CTEACHER）代表（课号，课名，教师）
* SC（SNO，CNO，SCGRADE）代表（学号，课号，成绩）
* 问题：1,找出没选过“黎明”老师的所有学生姓名。
* 2，列出2门以上（含2门）不及格学生姓名及平均成绩。
* 3，既学过1号课程又学过2号课程所有学生的姓名。
* 请用标准SQL语言写出答案。
*/
答案：
1,
select sname from s join sc on (s.sno = sc.sno) join c on (c.cno = sc.cno) where c.cteacher <> ‘黎明‘;

2,
--学生姓名
select sname from s where s.sno in ( select sno from sc where sc.scgrade < 60 group by sco having count(*) >=2 );
--平均成绩
select avg(scgrade) from sc where sc.sno in ( select sno from sc where sc.scgrade < 60 group by sco having count(*) >=2 ) group by sc.sno;

3,
select sname from s where s.sno in (select sno from sc where sc.cno =1 and sno in ( selcet distinct sno from sc where cno = 2 ) );


--
一个事务（transaction）起始于一条dml语句（insert，update，delete），终止于①commit语句；②ddl语句（create，drop）和dcl语句（grant，remove）；
正常断开连接时，transaction自动提交，非正常断开连接，transaction自动回滚。


--创建一张学生表    --约束类型：不为空约束，主键约束，外键约束，唯一性约束，check约束
create table stu1     --字段级约束条件
(
    id number(6),
    name varchar2(20) constraint stu_name_nn not null,--不为空约束
    sex number(1),
    age number(3),
    sdate date,
    grade number(2) default 1,
    class number(4) references class(id),--外键约束，外键约束被参考条件必须是主键
    email varchar2(50) unique --唯一约束条件
);

create table stu     
(
    id number(6) primary key,--主键约束
    name varchar2(20) constraint stu_name_nn not null,--不为空约束
    sex number(1),
    age number(3),
    sdate date,
    grade number(2) default 1,
    class number(4),
    email varchar2(50),
    constraint stu_name_email_uni unique(name,email),  --表级约束
    constraint stu_class_fk_foregin key (class) references class(id)
);

 
create table class
(
    id number(4) primary key,
    name varchar2(20) not null
);


alert table stu add(addr varchar2(100));

alert table stu drop (addr);

alert table stu modify (addr varchar2(120));

alert table stu add constraint stu_class_fk foreign key (class) references class(id);

--创建与删除索引
create index idx_stu_email on stu (email);


drop index idx_stu_email;
/



三范式：
①要有主键，列不可分；
②不能存在部分依赖；（联合主键情况下，非主键列不能部分依赖于主键）即每张表只描述一件事
③确保每列都和主键列直接相关，而不是间接相关。

--pl/sql结构化语言

--变量声明的规则：
1，变量名不能使用保留字，如from、select等；
2，第一个字符必须是字母；
3，变量名最多包含30个字符；
4，不要与数据库的表或者列同名；
5，每一行只能声明一个变量。

--常用变量类型：
1，binary_integer，整数，主要用来计数而不是用来表示字段类型；
2，number，数字类型；
3，char，定长字符串；
4，varchar2，变长字符串；
5，date，日期；
6，long，长字符串，最长2GB；
7，boolean，布尔类型，可以取值为true、false和null值。


--最简单的语句块
begin
    dbms_output.put_line(‘HelloWorld‘);
end;
/

在dos命令窗口输出命令：
set serveroutput on;

--简单的PL/SQL语句块
declare
    v_name varchar2(20);
begin
    v_name := ‘myname‘;
    dbms_output.put_line(v_name);
end;
/

--异常处理
declare
    v_num number := 0;
begin
    v_num := 2/v_num;
    dbms_output.put_line(v_num);
exception
    when others then
        dbms_output.put_line(‘error‘);
end;
/

--变量声明
declare
    v_temp number(1);
    v_count binary_integer := 0;
    v_sal number(7,2) := 4000.00;
    v_date date := sysdate;
    v_pi constant number(3,2) := 3.14;

    v_valid boolean := false;
    v_name varchar2(20) not null := ‘MyName‘;
begin
    dbms_output.put_line(‘v_temp value:‘ || v_sal);
end;
/
注意：dbms_output.put_line命令不能打印布尔类型。

--变量声明，使用%type属性
declare
    v_empno number(4);
    v_empno2 emp.empno%type;
    v_empno3 v_empno2%type;
begin
    dbms_output.put_line(‘Test‘);
end;
/

--Table变量类型，相当于java中的数组。
declare
    type type_table_emp_empno is table of emp.empno%type index by binary_integer;
    v_empnos type_table_emp_empno;

begin
    v_empnos(0) := 7369;
    v_empnos(2) := 7839;
    v_empnos(-1) := 9999;
    dbms_output.put_line(v_empnos(-1));
end;
/


--Table类型实例讲解

使用记录类型变量只能保存一行数据，这限制了SELECT语句的返回行数，如果SELECT语句返回多行就会错。Oracle提供了另外一种自定义类型，也就是表类型，它是对记录类型的扩展，允许处理多行数据，类似于表。
创建表类型的语法如下：
TYPE table_name IS TABLE OF data_type [ NOT NULL ]
INDEX BY BINARY_INTEGER ;
语法说明如下：
--table_name  创建的表类型名称。
--IS TABLE  表示创建的是表类型。
--data_type  可以是任何合法的PL/SQL数据类型，例如varchar2。
--INDEX BY BINARY_INTEGER  指定系统创建一个主键索引，用于引用表类型变量中的特定行。

使用表类型的例子：

 例一：直接对表类型变量赋值

declare
type my_emp is table of scott.emp%rowtype
index by binary_integer;
new_emp my_emp;
begin
new_emp(1).empno:=6800;
new_emp(1).ename:=‘tracy‘;
new_emp(1).job:=‘clerk‘;
new_emp(1).sal:=2500;
new_emp(2).empno:=6900;
new_emp(2).ename:=‘luck‘;
new_emp(2).job:=‘manager‘;
new_emp(2).sal:=4000;
dbms_output.put_line(new_emp(1).empno ||‘,‘||new_emp(1).ename||‘,‘||new_emp(1).job||
‘,‘||new_emp(1).sal);
dbms_output.put_line(new_emp(2).empno ||‘,‘||new_emp(2).ename||‘,‘||new_emp(2).job||
‘,‘||new_emp(2).sal);
end;
/

例二：使用表类型变量的方法：变量名.方法名[索引号]

declare
type my_emp is table of scott.emp%rowtype
index by binary_integer;
new_emp my_emp;
begin
new_emp(1).empno:=6800;
new_emp(1).ename:=‘tracy‘;
new_emp(1).job:=‘clerk‘;
new_emp(1).sal:=2500;
new_emp(2).empno:=6900;
new_emp(2).ename:=‘luck‘;
new_emp(2).job:=‘manager‘;
new_emp(2).sal:=4000;
dbms_output.put_line(new_emp.first||‘,‘||new_emp.count||‘,‘||new_emp.last);
dbms_output.put_line(new_emp(1).empno ||‘,‘||new_emp(1).ename||‘,‘||new_emp(1).job||
‘,‘||new_emp(1).sal);
dbms_output.put_line(new_emp(2).empno ||‘,‘||new_emp(2).ename||‘,‘||new_emp(2).job||
‘,‘||new_emp(2).sal);
--new_emp.delete(1);
dbms_output.put_line(new_emp.next(1));
end;
//

例三：与游标结合使用
declare
type my_emp is table of scott.emp%rowtype
index by binary_integer;
new_emp my_emp;
v_num number:=0;
cursor cur_emp is select empno,ename,job,sal from scott.emp;

begin
for v_emp in cur_emp loop
v_num:=v_num+1;
select * into new_emp(v_num) from scott.emp
where ename=v_emp.ename;
end loop;


for i in 1..new_emp.count loop
dbms_output.put_line(new_emp(i).empno ||‘,‘||new_emp(i).ename||‘,‘||new_emp(i).job||
‘,‘||new_emp(i).sal);
end loop;
end;
/
注意：不能直接对表变量赋值：select * into new_emp from scott.emp where deptno=30; 这种赋值方法是错的，赋值需要使用下标，如上面的的例子。




--Record变量类型
declare
    type type_record_dept is record
        (
            deptno dept.deptno%type,
            dname dept.dname%type,
            loc dept.loc%type
        );
        v_temp type_record_dept;
begin
    v_temp.deptno := 50;
    v_temp.dname := ‘aaaa‘;
    v_temp.loc := ‘bj‘;
    dbms_output.put_line(v_temp.deptno || ‘ ‘ || v_temp.dname);
end;
/

--使用%rowtype声明record变量
declare
    v_temp dept%rowtype;
begin
    v_temp.deptno := ‘50‘;
    v_temp.dname := ‘aaaa‘;
    v_temp.loc := ‘bj‘;
    dbms_output.put_line(v_temp.deptno || ‘ ‘ || v_temp.dname);
end;
/

--sql语句的运用
--select语句
declare
    v_ename emp.ename%type;
    v_sal emp.sal%type;
begin
    select ename,sal into v_ename,v_sal from emp where empno = 7369;
    dbms_output.put_line(v_ename || ‘ ‘ || v_sal);
end;
/
--select语句
declare
    v_emp emp%rowtype;
begin
    select * into v_emp from emp where empno = 7369;
    dbms_output.put_line(v_emp.ename);
end;
/

--insert语句
declare
    v_deptno dept.deptno%type := 50;
    v_dname dept.dname%type := ‘aaaa‘;
    v_loc dept.loc%type := ‘bj‘;
begin
    insert into dept values(v_deptno,v_dname,v_loc);
    commit;
end;
/

--update语句
declare
    v_deptno emp.deptno%type := 50;
    v_count number;
begin
    update emp set sal = sal/2 where deptno = v_deptno;
    --select deptno into v_deptno from emp where empno = 7369;
    --select count(*) into v_count from emp;
    dbms_output.put_line(sql%rowcount || ‘条记录被影响‘);
    commit;
end;
/
注意：sql代表刚刚执行过的语句，rowcount代表刚执行过的语句影响的记录。


--PL/SQL中执行DDL语句
begin
    execute immediate ‘create table T (nnn varchar2(20) default ‘‘aaa‘‘ )‘;
end;
/

--if语句
--取出7369的薪水，如果<1200，则输出‘low‘，如果<2000，则输出‘middle‘，否则‘high‘;
declare
    v_sal emp.sal%type;
begin
    select sal into v_sal from emp where empno = 7369;
    if(v_sal<1200) then
        dbms_output.put_line(‘low‘);
    elsif(v_sal<2000) then
        dbms_output.put_line(‘middle‘);
    else
        dbms_output.put_line(‘high‘);
    end if;
end;
/

--循环
--loop when循环,相当于java中的do..while循环
declare
    i binary_integer := 1;
begin
    loop
        dbms_output.put_line(i);
        i := i+1;
        exit when (i >= 11);
    end loop;
end;
/
--while循环
declare
    j binary_integer := 1;
begin
    while j < 11 loop
        dbms_output.put_line(j);
        j := j+1;
    end loop;
end;
/
--for循环
declare
    k binary_integer := 1;
begin
    for k in 1..10 loop
        dbms_output.put_line(k);
    end loop;
end;
/
declare
    k binary_integer := 1;
begin
    for k in reverse 1..10 loop       --逆序
        dbms_output.put_line(k);
    end loop;
end;
/

--错误处理
declare
    v_temp number(4);
begin
    select empno into v_temp from emp where deptno = 10;
exception
    when too_many_rows then
        dbms_output.put_line(‘太多记录了‘);
    when others then
        dbms_output.put_line(‘没数据‘);
end;
/

declare
    v_temp number(4);
begin
    select empno into v_temp from emp where empno = 2222;
exception
    when no_data_found then
        dbms_output.put_line(‘没数据‘);
end;
/
--创建错误日志
create table errorlog
(
    id number primary key,
    errcode number,
    errmsg varchar2(1024),
    errdate date
);
/
create sequence seq_errorlog_id start with 1 increment by 1;
/
declare
    v_deptno dept.deptno%type := 10;
    v_errcode number;
    v_errmsg varchar2(1024);
begin
    delete from dept where deptno = v_deptno;
    commit;
exception
    when others then
        rollback;
            v_errcode := SQLCODE;
            v_errmsg := SQLERRM;
        insert into errorlog values (seq_errorlog_id.nextval,v_errcode,v_errmsg,sysdate);
            commit;
end;
/

--游标
declare
    cursor c is                                   --声明游标
        select * from emp;
    v_emp c%rowtype;
begin
    open c;                                       --打开游标
    fetch c into v_emp;
    dbms_output.put_line(v_emp.ename);
    close c;                                      --关闭游标
end;
/
--游标，循环
declare
    cursor c is
        select * from emp;
    v_emp c%rowtype;
begin
    open c;
    loop
        fetch c into v_emp;
        exit when (c%notfound);
        dbms_output.put_line(v_emp.ename);
    end loop;
    close c;
end;
/
--while循环
declare
    cursor c is
        select * from emp;
    v_emp emp%rowtype;
begin
    open c;
    fetch c into v_emp;
    while (c%found) loop
        dbms_output.put_line(v_emp.ename);
        fetch c into v_emp;
    end loop;
    close c;
end;
/
--for循环
declare
    cursor c is
        select * from emp;
begin
    for v_emp in c loop
        dbms_output.put_line(v_emp.ename);
    end loop;
end;
/
--带参数的游标
declare
    cursor c(v_deptno emp.deptno%type, v_job emp.job%type)
    is
        select ename,sal from emp where deptno = v_deptno and job = v_job;
begin
    for v_temp in c(30,‘CLERK‘) loop
        dbms_output.put_line(v_temp.ename);
    end loop;
end;
/
--可更新的游标
declare
    cursor c
    is
        select * from emp2 for update;
begin
    for v_temp in c loop
        if (v_temp.sal < 2000) then
            update emp2 set sal = sal * 2 where current of c;
        elsif (v_temp.sal = 5000) then
            delete from emp2 where current of c;
        end if;
    end loop;
    commit;
end;
/



--oracle集合类型的first、next、prior、 last方法

创建一个存储过程，用于产生oracle三种集合类型的数据
 
create or replace procedure plch_main
is
  TYPE NESTED_T      IS TABLE  OF NUMBER;--嵌套表类型
  TYPE ASSOCIATIVE_T IS TABLE  OF NUMBER  INDEX BY BINARY_INTEGER; --索引表类型
  TYPE VARRAYS_T     IS VARRAY(10) OF NUMBER; --变长数组类型
  
  lst_nested nested_t:=nested_t(-2000,null,3500);
  lst_associative associative_t;--索引表类型的集合不能直接赋值 可以从其特性来理解（可以是稀疏排列的）
  lst_varrays varrays_t:=varrays_t(-2000,null,3500);
begin
 
  lst_associative(1):=-2000;
  lst_associative(3):=null;--注意，这里没有lst_associative数组第二个元素
  lst_associative(4):=3500;
 
  dbms_output.put_line(‘以下为嵌套表的输出内容：‘);
  dbms_output.put_line(‘lst_nested(1)     :‘||lst_nested(1));
  dbms_output.put_line(‘lst_nested(2)     :‘||lst_nested(2));
  dbms_output.put_line(‘lst_nested(3)     :‘||lst_nested(3));
  dbms_output.put(‘lst_nested.first-1:‘);  
  dbms_output.put_line(lst_nested.first-1);
  dbms_output.put_line(‘lst_nested.first  :‘||lst_nested.first);
  dbms_output.put_line(‘lst_nested.prior(1):‘||lst_nested.prior(1));
  dbms_output.put_line(‘lst_nested.next(1):‘||lst_nested.next(1));
  dbms_output.put_line(‘lst_nested.next(2):‘||lst_nested.next(2));
  dbms_output.put_line(‘lst_nested.next(3):‘||lst_nested.next(3));
  dbms_output.put_line(‘lst_nested.last   :‘||lst_nested.last);
  
  dbms_output.put_line(‘以下为索引表的输出内容：‘);  
  dbms_output.put_line(‘lst_associative(1)     :‘||lst_associative(1));
  dbms_output.put_line(‘lst_associative(3)     :‘||lst_associative(3));
  dbms_output.put_line(‘lst_associative(4)     :‘||lst_associative(4));
  dbms_output.put(‘lst_associative.first-1:‘);
  dbms_output.put_line(lst_associative.first-1);
  dbms_output.put_line(‘lst_associative.first  :‘||lst_associative.first);
  dbms_output.put_line(‘lst_associative.prior(1):‘||lst_associative.prior(1));
  dbms_output.put_line(‘lst_associative.next(1):‘||lst_associative.next(1));
  dbms_output.put_line(‘lst_associative.next(2):‘||lst_associative.next(2));
  dbms_output.put_line(‘lst_associative.next(4):‘||lst_associative.next(4));
  dbms_output.put_line(‘lst_associative.last   :‘||lst_associative.last);
  
  dbms_output.put_line(‘以下为变长数组的输出内容：‘);
  dbms_output.put_line(‘lst_varrays(1)     :‘||lst_varrays(1));
  dbms_output.put_line(‘lst_varrays(2)     :‘||lst_varrays(2));
  dbms_output.put_line(‘lst_varrays(3)     :‘||lst_varrays(3));
  dbms_output.put(‘lst_varrays.first-1:‘);
  dbms_output.put_line(lst_varrays.first-1);
  dbms_output.put_line(‘lst_varrays.first  :‘||lst_varrays.first);
  dbms_output.put_line(‘lst_varrays.prior(1):‘||lst_varrays.prior(1));
  dbms_output.put_line(‘lst_varrays.next(1):‘||lst_varrays.next(1));
  dbms_output.put_line(‘lst_varrays.next(2):‘||lst_varrays.next(2));
  dbms_output.put_line(‘lst_varrays.next(3):‘||lst_varrays.next(3));
  dbms_output.put_line(‘lst_varrays.last   :‘||lst_varrays.last);
end;
/
 
存储过程编译成功，以下调用并查看结果。
特别注意三种数组中第一个元素的prior方法、最后一个元素的next方法都是可以执行出来的；
并且索引表类型中未定义的元素序列也有prior、next方法。
 
SQL> exec plch_main;
 
以下为嵌套表的输出内容：
lst_nested(1)     :-2000
lst_nested(2)     :
lst_nested(3)     :3500
lst_nested.first-1:0
lst_nested.first  :1
lst_nested.prior(1):
lst_nested.next(1):2
lst_nested.next(2):3
lst_nested.next(3):
lst_nested.last   :3
以下为索引表的输出内容：
lst_associative(1)     :-2000
lst_associative(3)     :
lst_associative(4)     :3500
lst_associative.first-1:0
lst_associative.first  :1
lst_associative.prior(1):
lst_associative.next(1):3
lst_associative.next(2):3
lst_associative.next(4):
lst_associative.last   :4
以下为变长数组的输出内容：
lst_varrays(1)     :-2000
lst_varrays(2)     :
lst_varrays(3)     :3500
lst_varrays.first-1:0
lst_varrays.first  :1
lst_varrays.prior(1):
lst_varrays.next(1):2
lst_varrays.next(2):3
lst_varrays.next(3):
lst_varrays.last   :3
 
PL/SQL procedure successfully completed
 
.first方法是数组中第一个元素的下标值（序列值）
.prior(n)方法是数组中第n个元素的前一个元素的下标值（序列值）