PL/SQL常用語句

面向過程的語言
--最簡單的語句塊
//:=代表賦值;  =代表相等
set serveroutput on;
begin
  dbms_output.put_line('helloworld!');
end;

--簡單PL/SQL語句塊
declare
  v_name varchar2(20);
begin
  v_name := 'myname';
  dbms_output.put_line(v_name);
end;

--完整語句塊組成
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;

--變量聲明規則
1，變量名不能使用保留字，如 from,select等
2，第一個字符必須是字母
3，變量名最多包含三十個字符
4，不要與數據庫的表或者列同名
5，每一行只能聲明一個變量
--常用變量類型
1，binary_integer:整數，主要用來計數而不是用來表示字段類型
2，number：數字類型
3，char:定長字符串
4，varchar2：變長字符串
5，date:日期
6，long:長字符串，最長 2GB
7, boolean:布爾類型，可以取值爲 true,false 和 null值

declare
  v_temp number(1);
  v_count binary_integer := 0;
  v_sal number(7,2) := 4000.00;
  v_date date := sysdate;
  v_date2 date ;
  v_pi constant number(3,2) := 3.14;
  v_valid boolean := false;
  v_name varchar2(20) not null := 'myname';
begin
  v_date2 := to_date('1999-08-12 12:23:38','YYYY-MM-DD HH24:MI:SS');
  dbms_output.put_line('v_temp value:' || v_count);
  end;
--變量聲明,使用 %type 屬性
declare
  v_empno number(4);
  v_empno2 emp.empno%type;
  v_empno3 v_empno2%type;
begin
  dbms_output.put_line('test');
end;

                     符合變量
--table 變量類型//相當於Java中的數組
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;

--record 變量類型//相當於Java中的類
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 聲明 record 變量
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;

                          DML語句
--使用select 語句//必須和into一起使用,必須有且只有一條記錄返回
declare
  v_ename emp.ename%type;
  v_sal emp.sal%type;
begin
  select ename,sal into v_ename,v_sal from emp when empno = 7369;
  dbms_output.put_line(v_ename || ' ' || v_sal);
end;
declare
  v_emp emp%rowtype;
begin
  select * into v_emp from emp when ename = 7369;
  dbms_output.put_line(v_emp.ename);
end;  
                    
--insert 語句
declare
  v_deptno 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;
end;

--update語句
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;//一條記錄被影響
  --select count(*) into v_count from emp2;//一條記錄被影響
  dbms_output.put_line(sql%rowcount || '條記錄被影響');//sql代表剛剛執行的那條語句，rowcount代表sql影響的記錄條數
  commit;
end;

                   DDL語句//執行DDL語句需要加 execute immediate
begin
  execute immediate 'create table T (nnn varchar2(20) default ''aaa'')';//''爲兩個單引號
end;

--if語句
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;

--循環語句
declare
  i binary_integer := 1;
begin
  loop//相當於Java中的do-while循環
    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 //相當於Java中的while循環
    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//reverse代表逆序
    dbms_output.put_line(k);
  end loop;
end;
                    
--錯誤處理
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('太多記錄了’);
  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('沒數據');
end;

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;//SQLCODE爲關鍵字，出錯代碼
    v_errmsg := SQLERRM;//SQLERRM爲關鍵字，出錯信息
    insert into errorlog values (seq_errorlog_id.nextval,v_errcode,v_errmsg,sysdate);
    commit;
end;
--cursor(遊標)//重點掌握
declare
  cursor c is
    select * from emp;
  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;
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;

declare
  cursor c is
    select * from emp;
  v_emp c%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;

declare//最常用
  cursor c is
    select * from emp;
begin
  for v_emp in c loop
    dbms_output.put_line(v_emp.ename);
  end loop;
end;

--帶參數的遊標
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;
  --v_temp c%rowtype;
begin
  for v_emp in c(30,'CLERK') loop
    dbms_output.put_line(v_emp.ename);
  end loop;
end;

--可更新的遊標
declare//最常用
  cursor c is
    select * from emp for update;
  --v_temp c%rowtype;
begin
  for v_emp 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;
end;

--存儲過程(stored procedure)
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;
    elsif (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;
調用過程方法一
begin
  p;
end;
調用過程方法二
exec p;

--帶參數的存儲過程
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;

--函數
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;

--觸發器(trigger)
create table emp2_log
(
  uname varchar2(20),
  action varchar2(10),
  atime date
);

create or replace trigger trig
  after insert or delete or update on emp2 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;

select * from emp2_log;

update emp2 set deptno = 99 where deptno =          10;//此語句出錯,違反完整約束條件
 
drop trigger trig;

create or replace trigger trig//附加功能,不常用
  after update on dept for each row
begin
  update emp set deptno = :NEW.deptno where deptno = :OLD.deptno;
end;

select * from emp;

rollback;

--樹狀結構的存儲和展示
drop table article;
 
create table article
(
  id number primary key,
  cont varchar2(4000),
  pid number,
  isleaf number(1),  --0代表非葉子節點，1代表葉子節點
  alevel number(2)
);

insert into article values (1,'螞蟻大戰大象',0,0,0);
insert into article values (2,'大象被打趴下了',1,0,1);
insert into article values (3,'螞蟻也不好過',2,1,2);
insert into article values (4,'瞎說',2,0,2);
insert into article values (5,'沒有瞎說',4,1,3);
insert into article values (6,'怎麼可能',1,0,1);
insert into article values (7,'怎麼沒有可能',6,1,2);
insert into article values (8,'可能性是很大的',6,1,2);
insert into article values (9,'大象進醫院了',2,0,2);
insert into article values (10,'護士是螞蟻',9,1,3);

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.id,v_level + 1);
    end if;
  end loop;
end;