Oracle游标（光标）

表、select语句、游标：返回结果都能是一个集合。

注意：游标的结果是一个集合。

--查询并打印员工的姓名和薪水
set serveroutput on
/*
光标:
1. 光标的属性： %isopen    %rowcount(返回的行数)
              %notfound  %found

2. 默认情况下。一次性打开300个光标
SQL> show parameter  cursor

NAME                                 TYPE        VALUE
------------------------------------ ----------- ---------------
cursor_sharing                       string      EXACT
cursor_space_for_time                boolean     FALSE
open_cursors                         integer     300
session_cached_cursors               integer     20

改动光标:
alter system set open_cursors=400;
*/
declare
  --定义一个光标
  cursor cemp is select ename,sal from emp;
  pename emp.ename%type;引用变量
  psal   emp.sal%type;引用变量
begin
  open cemp;
  loop
    --取一条记录
    fetch cemp into pename,psal;
    --退出： fetch没有取到
    exit when cemp%notfound;
    
    dbms_output.put_line(pename||'的薪水是'||psal);
  
  end loop;
  close cemp;
end;
/

--查询某个部门的员工姓名
set serveroutput on

declare
  cursor cemp(dno number) is select ename from emp where deptno=dno;
  pename emp.ename%type;
begin
  open cemp(20);
  loop
    fetch cemp into pename;
    exit when cemp%notfound;
    
    dbms_output.put_line(pename);

  end loop;
  close cemp;
end;
/

/*
SQL语句
select to_char(hiredate,'YYYY') from emp
--> 光标 --> 循环 --> 退出条件

变量:
count80 number := 0;
count81 number := 0;
count82 number := 0;
count87 number := 0;
*/
set serveroutput on
declare
  cursor cemp is select to_char(hiredate,'YYYY') from emp;
  phiredate varchar2(4);
  
  count80 number := 0;
  count81 number := 0;
  count82 number := 0;
  count87 number := 0;
begin
  open cemp;
  loop
    --取一个员工的年份
    fetch cemp into phiredate;
    exit when cemp%notfound;
    
    --推断年份
    if phiredate = '1980' then count80 := count80+1;
      elsif phiredate = '1981' then count81 := count81+1;
      elsif phiredate = '1982' then count82 := count82+1;
      else count87 := count87 + 1;
    end if;
  end loop;
  close cemp;
  
  --输出
  dbms_output.put_line('Total:'||(count80+count81+count82+count87));
  dbms_output.put_line('1980:'||count80);
  dbms_output.put_line('1981:'||count81);
  dbms_output.put_line('1982:'||count82);
  dbms_output.put_line('1987:'||count87);
end;
/
   
  

/*
SQL语句:
select empno,sal from emp order by sal
--> 光标 --> 循环  --> 退出条件: 1. 总额> 5w  2. 全部人涨完

变量:
涨工资的人数： countEmp number := 0;
涨后的工资总额: salTotal number;
                1. select sum(sal) into salTotal from emp;
                2. 涨后 = 涨前 + sal * 0.1

练习： 工资总额不能超过5w                
*/
set serveroutput on
declare
  cursor cemp is select empno,sal from emp order by sal;
  pempno emp.empno%type;
  psal   emp.sal%type;
  --涨工资的人数： 
  countEmp number := 0;
  
  --涨后的工资总额: 
  salTotal number;
begin
  --得到工资初始值
  select sum(sal) into salTotal from emp;
  open cemp;
  loop
    --1. 总额> 5w 
    exit when salTotal > 50000;
    --取一个员工
    fetch cemp into pempno,psal;
    --2. 全部人涨完
    exit when cemp%notfound;
    
    --涨工资
    update emp set sal=sal*1.1 where empno=pempno;
    --人数+1
    countEmp := countEmp +1;
    --总额
    salTotal := salTotal + psal * 0.1;
  end loop;
  close cemp;
  
  commit;
  dbms_output.put_line('人数:'||countEmp||'   涨后的工资总额:'||salTotal);
end;
/  
  
  

/*
SQL语句:
部门: select deptno from dept --> 光标 --> 循环  --> 退出条件
部门中员工的薪水: select sal from emp where deptno=?? 
                  --> 带參数的光标 --> 循环  --> 退出条件

变量:
每一个段的人数:
count1 number; count2 number; count3 number;
部门的工资总额:
salTotal number;
1. 累加
2. select sum(sal) into salTotal from emp where deptno=?
?

*/
set serveroutput on
declare
  --部门
  cursor cdept is select deptno from dept;
  pdeptno dept.deptno%type;

  --部门中员工的薪水
  cursor cemp(dno number) is select sal from emp where deptno=dno;
  psal emp.sal%type;
  
  --每一个段的人数:
  count1 number; count2 number; count3 number;

  --部门的工资总额:
  salTotal number;
begin
  open cdept;
  loop
    --取一个部门
    fetch cdept into pdeptno;
    exit when cdept%notfound;
    --初始化
    count1:=0; count2:=0; count3:=0;
    --部门的工资总额
    select sum(sal) into salTotal from emp where deptno=pdeptno;
    --部门中员工的薪水
    open cemp(pdeptno);
    loop
      -- 取一个员工的薪水
      fetch cemp into psal;
      exit when cemp%notfound;
      
      --推断薪水
      if psal < 3000 then count1:=count1+1;
        elsif psal>=3000 and psal< 6000 then count2:=count2+1;
        else count3:=count3+1;
      end if;
    
    end loop;
    close cemp;

    --保存当前部门
    insert into msg values(pdeptno,count1,count2,count3,nvl(salTotal,0));

  end loop;
  close cdept;
  commit;
  
  dbms_output.put_line('完成');
end;
/