pl/sql学习笔记---马士兵教程38-48

时间:2023-03-08 19:59:54

Procedure Language/Structure query Language

一、关于语言学习

  1、数据类型 2、语法   通过例子来学习很快就能明白

  set serverputout on;

  begin

    dbms_output.put_line(‘HelloWorld!’);

  end;

二、结构(declare(可选)、begin、exception(可选)、end)

  1、declare例子

    declare

      v_name varchar2(20);

    begin

      v_name := 'MyName';

      dbms_output.put_line(v_name);

    end;

  2、exception例子

    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;

三、数据类型

  1、常用变量类型

   (1)、binary_integer:整数,主要用于计数而不是用于表示字段类型。

   (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:true,false和null

  例子:

  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_temp);

  end;

  --变量声明,使用%type属性

  例子:

  declare

    v_empno number(4);

    v_empno2 emp.empno%type;

    v_empno3 v_empno%type;

  begin

    dbms_output.put_line('Test');

  end;

  2、复杂数据类型(table相当于java里的数组,record相当于java中的类)

  --Table变量类型

  例子  

  declare

    type type_table_emp_empno is table of  emp.empno%type index by binary_integer;

    v_empnos type_table_empno;

  begin

    v_empnos(0) := 7369;

    v_empnos(2) := 7839;

    v_empnos(-1) := 9999;

    dbms_output.put_line(v_empnos(-1));

  end;

  --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(有助于程序维护)

  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_e_temp.dname);

  end;

四、SQL语句的运用

  例子:

  declare

    v_ename emp.ename%type;

    v_sal emp.sal%type;

  begin

    select ename , sal  into v_name , v_sal from emp where empno = 7369;

    dbms_output.put_line(v_name || ' ' || v_sal);

  end;

  <注>:sql语句中,select语句必须与into一起用,且返回记录有且仅有一条

  declare

    v_temp emp%rowtype;

  begin

    select * into v_emp from emp where empno = 7360;

    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;

  end;

  declare

    v_deptno emp2.deptno%type := 10;

    v_count number;

  begin

    --update emp2 set  sal = sal/2 wehre deptno = v_deptno;

    --select deptno into v_daptno from emp2 where empno = 7369;

    select count(*) into v_count from emp2;

    dbms_output.put_line(sql%rowcount || '条记录被影响');

    commit;

  end;

  DDL语句

  begin

    execute immediate 'create table T mmm varchar2(20) default ''aaa'');

  end;

  3、分支与循环

  --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');

    elseif(v_sal<2000) then

      dbms_output.put_line('Middle');

    else

      dbms_output.put_line('High');

    end if;

  end;

  --循环

  --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

  begin  

     for k in 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.put_line('太多记录了');

    when no_data_found then

      dbms_output.put_line('没数据');

    when otheres then

      dbms_output.put_line('error');

  end;

  --数据库报错记录 Log  

  create table errorlog

  (

    id number primary key,

    errcode number,

    errmsg varchar2(1024),

    errdate date

  );

  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 (java里的iterater)  fetch 移动游标

  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;

 --遍历游标的三种方式

  (1)、do-while方式

  declare

    cursor c is select * from emp;

    v_emp c%rowtype;

  begin

    open c;

    loop

      fetch c into v_empl;

      exit when (c%notfound);

      dbms_output.put_line(v_emp.ename);

    end loop;

    close c;

  end;

  (2)、while方式

  declare

    curser 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;

  (3)、For循环方式

  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;

      elseif(v_temp.sal = 5000) then

        delete from emp where current of c;

      end if;

    end loop;

    commit;

  end;