学步园

PL_SQL：带有分支和循环,面向过程

匿名块：

declare(可选，声明各种变量和游标的地方)
begin(必要的，从此开始执行)
exception(抓取到异常后执行的)
end;

set serveroutput on;(默认是关闭)
--最简单的PL/SQL语句块
begin
  dbms_output.put_line('HelloWorld!');
end;
--最简单的语句块
declare
   v_name varchar2(20);
begin
  v_name := 'myname';
  dbms_output.put_line(v_name);
end;
--语句块的组成
declare
  v_name number := 0;
begin
  v_name := 2/v_num;
  dbms_output.put_line(v_name);
  exception
    when others then
      dbms_output.put_line('error');
end;

--变量声明

1.  变量名不能够使用保留字，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，效率高
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ture、false和null值，一定要给初值，无法打印

--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_count);
end;

--变量声明，使用%type属性

/*注释多行*/ --注释一行
declare
  v_empno number(4);
  v_empno2 emp.empno%type;--用表内字段类型声明变量类型
  v_empno3 v_empno2%type;--用变量type属性声明变量类型
begin
  dbms_output.put_line('Test');
end;

--简单变量赋值

declare
  v_name varchar2(20);
  v_sal number(7,2);
  v_sal2 number(7,2);
  v_valid boolean := false;
  v_date date;
begin
  v_name := 'MyName';
  v_sal := 23.77;
  v_sal2 := 23.77;
  v_valid := (v_sal = v_sal2);--判断是否相等用=
  v_date := to_date('1999-08-12 12:23:30','YYYY-MM-DD HH24:MI:SS');
end;

--Table变量类型，表示一个数组

declare
  type type_table_emp_empno is table of emp.empno%type index by binary_integer;--首先声明一个类型
  v_empnos type_table_emp_empno;--再用这个类型声明变量
begin
  v_empnos(0) := 7369;
  v_empnos(2) := 7839;
  v_empnos(-1) := 9999;
  dbms_output.put_line(v_empnos(-1));---1访问不到，0,2可以访问到
end;

--Record类型，表示一个类

declare
   type type_record_dept is record
   (
    deptno dept.deptno%type,
    dname dept.dname%tpye,
    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;

--PL/SQL里执行select语句的话，配合into，必须返回并只能返回一条记录
--SQL语句的运用

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(ename || ' ' || v_sal);
end;

declare
  v_emp emp%rowtype;
begin
 select * into v_emp from emp where empno = 7369;
 dbms_output.put_line(v_emp.ename);
end;

declare
  v_deptno dept.deptno%type := 50;
  v_dname dept.dname%type := 'aaaa';
  v_loc dept.loc%type := 'bj';
begin
  insert into dept2 values(v_deptno,v_dname,v_loc);
  commit;--别忘了!!!
end;

select * from dept2;

declare
  v_deptno emp2.deptno%type := 10;
  v_count number;
begin
  --update emp2 set sal = sal/2 where deptno = v_deptno;
  --select deptno into v_deptno from emp2 where empno = 7369;
  select count(*) into v_count from emp2;
  dbms_output.put_line(sql%rowcount || '条记录被影响');//sql,关键字，代表刚刚执行的sql程序
end;

--PL/SQL执行DDL语句,需要加execute immediate

begin
  execute immediate 'create table T(nnn varchar2(20) default ''aaaa'')';
end;

--if语句

--取出7369的薪水，如果<1200，则输出'low'，如果<2000则输出'middle'，否则输出'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 --elsif没e
    dbms_output.put_line('midddle');
  else
    dbms_output.put_line('high');
  end if;
end;

--循环

declare
  i binary_integer := 1;
begin
  loop
    dbms_output.put_line(i);
    i := i + 1;
    exit when (i >= 11);
 end loop;
end;

declare
 j binary_integer := 1;
begin
  while j < 11 loop
    dbms_output.put_line(j);
    j := j + 1;
  end loop;
end;

begin
  for k in 1..10 loop
    dbms_output.put_line(k);
  end loop;
 
  for k in reverse 1..10 loop
    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.putline('太多记录了');
  when others then
    dbms_output.put_line('error');
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('没有数据');
end;

--sql程序跨数据库平台较好，PL/SQL效率高

--DBA，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cursor，结果集上的指针

declare
  cursor c is
    select * from emp;--只是声明游标，还未取数据
  v_emp c%rowtype
begin
  open c;
  fetch c into v_emp;
  dbms_output.put_line(v_emp.ename);
  close c;
end;

declare
  cursor c is
    select * from emp;
  v_emp c%rowtype;
beigin
  open c;
  loop
    fetch c into v_emp;
    exit when (c%notfound);
    dbms_output.put_line(v_emp.ename);
  end loop;
  close c;
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;
    else if (v_temp.sal = 5000) then
      delete from emp2 where current of c;
    end if;
  end loop;
  commit;
end;

--创建存储过程，带有名字的PL/SQL块

grant create procedure to shijin;
create or replace procedure p
is
  cursor c is
    select * from emp2 for update;
begin
  for v_emp in c loop
    if(v_emp.deptno = 10) then
      update emp2 set sal = sal + 10 where current of c;
    else if (v_emp.deptno = 20) then
      update emp2 set sal = sal + 20 where current of c;
    else
      update emp2 set sal = sal + 50 where current of c;
    end if;
  end loop;
  commit;
end loop;

begin
  p;
end;
或者
exec p;

--带参数的存储过程，默认是in

create or replace procedure p
  (v_a in number,v_b number,v_ret out number,v_temp in out number)
is

begin 
  if (v_a > v_b) then
    v_ret := v_a;
  else
    v_ret := v_b;
  end if;
  v_temp := v_temp + 1;
end;

declare
  v_a number := 3;
  v_b number := 4;
  v_ret number;
  v_temp number := 5;
begin
  p(v_a,v_b,v_ret,v_temp);
  dbms_output.put_line(v_ret);
  dbms_output.put_line(v_temp);
end;

--函数

create or replace function sal_tax
  (v_sal number)
  return number
is
begin
  if(v_sal < 2000) then
    return 0.10;
  elsif(v_sal < 2750) then
    return 0.15;
  else
    return 0.20;
  end if;
end;

select sal_tax(sal) from emp;

--触发器！！！！牢牢掌握概念

create table emp2_log
(
  uname varchar2(20),
  action varchar2(10),
  atime date
);
grant create triger to shijin;
create or replace trigger trig
  after insert or delete or update on emp2 --此处可以加上for each row
begin
  if inserting then
    insert into emp2_log values (USER,'insert',sysdate);
  elsif updating then
    insert into emp2_log values (USER,'update',sysdate);
  elsif deleting then
    insert into emp2_log values (USER,'delete',sysdate);
  end if;
end;

update emp2 set sal = sal*2 where deptno = 30;

drop trigger trig;

create or replace trigger trig
  after update on dept
  for each row
begin
  update emp set deptno = :NEW.deptno where deptno = :OLD.deptno;
end;

--树状结构数据的存储与显示

drop table article;

create table article
(
  id number primary key,
  cont varchar2(4000),
  pid number,
  isleaf number(1),--0代表非叶子节点，1代表叶子节点
  alevel number(2)
)

create or replace procedure p (v_pid article.pid%type,v_level binary_integer) is
  cursor c is select * from article where pid = v_pid;
  v_preStr varchar2(1024) := '';
begin
  for i in 1..v_level loop
    v_preStr := v_preStr || '****';
  end loop;
  for v_article in c loop
    dbms_output.put_line(v_preStr || v_article.cont);
    if(v_article.isleaf = 0) then
      p(v_articel.id,v_level + 1);
    end if;
  end loop;
end;
insert into article values (1,'蚂蚁大战大象',0,0,0);
insert into article values (2,'大象被打趴下',1,0,1);
insert into article values (3,'蚂蚁也不好过',2,1,2);
insert into article values (4,'瞎        说',2,0,2);
insert into article values (5,'没 有 瞎  说',4,1,3);
insert into article values (6,'怎 么 可  能',1,0,1);
insert into article values (7,'怎么没有可能',6,1,2);
insert into article values (8,'可能性很大的',6,1,2);
insert into article values (9,'大象进医院了',2,0,2);
insert into article values (10,'护士是蚂蚁',9,1,3);

set serverout on;
begin
  p(0,0);
end;
show error;
--展示emp的树状结构