一. 使用for循环游标：遍历全部职位为经理的雇员

1. 定义游标(游标就是一个小集合)

2. 定义游标变量

3. 使用for循环游标

declare
  -- 定义游标c_job
  cursor c_job is
    select empno, ename, job, sal from emp where job = ‘MANAGER‘;
    
  -- 定义游标变量c_row
  c_row c_job%rowtype;
begin
  -- 循环游标，用游标变量c_row存循环出的值
  for c_row in c_job loop
    dbms_output.put_line(c_row.empno || ‘-‘ || c_row.ename || ‘-‘ ||
                         c_row.job || ‘-‘ || c_row.sal);
  end loop;
end;

二. fetch游标：遍历全部职位为经理的雇员

使用的时候必须明白的打开和关闭

declare
  --定义游标c_job
  cursor c_job is
    select empno, ename, job, sal from emp where job = ‘MANAGER‘;

  --定义游标变量c_row
  c_row c_job%rowtype;
begin
  open c_job;
  loop
    --提取一行数据到c_row
    fetch c_job into c_row;
    
    --判读是否提取到值。没取到值就退出
    exit when c_job%notfound;
    dbms_output.put_line(c_row.empno || ‘-‘ || c_row.ename || ‘-‘ ||
                         c_row.job || ‘-‘ || c_row.sal);
  end loop;
  
  --关闭游标
  close c_job;
end;

三. 使用游标和while循环：遍历全部部门的地理位置

--3,使用游标和while循环来显示全部部门的的地理位置（用%found属性）
declare
  --声明游标
  cursor csr_TestWhile is select loc from dept;

  --指定行指针
  row_loc csr_TestWhile%rowtype;
begin
  open csr_TestWhile;
  --给第一行数据
  fetch csr_TestWhile into row_loc;
  
  --測试是否有数据，并运行循环
  while csr_TestWhile%found loop
    dbms_output.put_line(‘部门地点：‘ || row_loc.LOC);
    --给下一行数据
    fetch csr_TestWhile into row_loc;
  end loop;
  close csr_TestWhile;
end;

四. 带參的游标：接受用户输入的部门编号

declare
  -- 带參的游标
  cursor c_dept(p_deptNo number) is
    select * from emp where emp.deptno = p_deptNo;
    
  r_emp emp%rowtype;
begin
  for r_emp in c_dept(20) loop
    dbms_output.put_line(‘员工号：‘ || r_emp.EMPNO || ‘员工名：‘ 
                         || r_emp.ENAME || ‘工资：‘ || r_emp.SAL);
  end loop;
end;

五. 加锁的游标：对全部的salesman添加佣金500

declare
  --查询数据，加锁(for update of)
  cursor csr_addComm(p_job nvarchar2) is
    select * from emp where job = p_job for update of comm;
  r_addComm emp%rowtype;
  commInfo  emp.comm%type;
begin
  for r_addComm in csr_addComm(‘SALESMAN‘) loop
    commInfo := r_addComm.comm + 500;
    
    --更新数据(where current of)
    update emp set comm = commInfo where current of csr_addComm;
  end loop;
end;

declare
  cursor crs_testComput is
    select * from emp order by hiredate asc;
    
  --计数器
  top_two      number := 2;
  r_testComput crs_testComput%rowtype;
begin
  open crs_testComput;
  fetch crs_testComput into r_testComput;
  while top_two > 0 loop
    dbms_output.put_line(‘员工姓名：‘ || r_testComput.ename ||
                         ‘ 工作时间：‘ || r_testComput.hiredate);
    --计速器减1
    top_two := top_two - 1;
    fetch crs_testComput into r_testComput;
  end loop;
  close crs_testComput;
end;

declare
  cursor crs_upadateSal is
    select * from emp for update of sal;
  r_updateSal crs_upadateSal%rowtype;
  salAdd      emp.sal%type;
  salInfo     emp.sal%type;
begin
  for r_updateSal in crs_upadateSal loop
    salAdd := r_updateSal.sal * 0.2;
    if salAdd > 300 then
      salInfo := r_updateSal.sal;
      dbms_output.put_line(r_updateSal.ename || ‘:  加薪失败。‘ ||
                           ‘薪水维持在：‘ || r_updateSal.sal);
    else
      salInfo := r_updateSal.sal + salAdd;
      dbms_output.put_line(r_updateSal.ENAME || ‘:  加薪成功.‘ ||
                           ‘薪水变为：‘ || salInfo);
    end if;
    update emp set sal = salInfo where current of crs_upadateSal;
  end loop;
end;

declare
  cursor crs_caseTest is
    select * from emp for update of sal;

  r_caseTest crs_caseTest%rowtype;
  salInfo    emp.sal%type;
begin
  for r_caseTest in crs_caseTest loop
    case
      when r_caseTest.deptno = 10 THEN
        salInfo := r_caseTest.sal * 1.05;
      when r_caseTest.deptno = 20 THEN
        salInfo := r_caseTest.sal * 1.1;
      when r_caseTest.deptno = 30 THEN
        salInfo := r_caseTest.sal * 1.15;
      when r_caseTest.deptno = 40 THEN
        salInfo := r_caseTest.sal * 1.2;
    end case;
    update emp set sal = salInfo where current of crs_caseTest;
  end loop;
end;

九. 异常处理：数据回滚

set serveroutput on;
declare
  d_name varchar2(20);
begin
  d_name := ‘developer‘;
  
  savepoint A;
  insert into DEPT values (50, d_name, ‘beijing‘);
  savepoint B;
  insert into DEPT values (40, d_name, ‘shanghai‘);
  savepoint C;
  
  exception when others then
    dbms_output.put_line(‘error happens‘); 
	  rollback to A;
  commit;
end;
/

十. 基本指令：

set serveroutput on size 1000000 format wrapped; --使DBMS_OUTPUT有效,并设置成最大buffer,防止"吃掉"最前面的空格
set linesize 256; --设置一行能够容纳的字符数
set pagesize 50; --设置一页有多少行数
set arraysize 5000; --设置来回数据显示量,这个值会影响autotrace时一致性读等数据
set newpage none; --页和页之间不设不论什么间隔
set long 5000; --LONG或CLOB显示的长度
set trimspool on; --将SPOOL输出中每行后面多余的空格去掉
set timing on; --设置查询耗时
col plan_plus_exp format a120; --autotrace后explain plan output的格式
set termout off; --在屏幕上暂不显示输出的内容,为以下的设置sql做准备
alter session set nls_date_format=‘yyyy-mm-dd hh24:mi:ss‘; --设置时间格式

以下的语句一定要在Command Window里面才干打印出内容

set serveroutput on;
begin 
dbms_output.put_line(‘hello!‘);
end;
/