游标PLSQL/SQL引撑切换在什么情况下发生?

2012-07-31 09:53:37 165 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

只听说过使用游标会发生切换所以采用批量BULK 方法
下面4种情况使用游标的方法哪种会发生切换还是全部分会发生切换?
1



  Declare

     Cursor myCur is select ename,job,sal,empno from emp;

     varE myCur%rowType;

  Begin

     open myCur;

     loop

        fetch myCur into varE;

        exit when myCur%notfound;

        dbms_output.put_line(myCur%rowCount||'    '||vare.empno||'    '||vare.ename||'    '||vare.sal);

     end loop;

  End



 Declare

     Cursor myCur is select * from emp;

   varE myCur%rowType;

  Begin

     for varA in myCur

      loop

         select ename,job,sal,empno  into varE from emp where empno= vara.empno;

         dbms_output.put_line(vare.empno||'    '||vare.ename||'    '||vare.sal);

      end loop;

  End;

 

  Declare

     Cursor myCur is select ename,job,sal from emp;

     type type_ename  is table of emp.ename %type index by binary_integer;

     type type_job  is table of emp.job %type index by binary_integer;

     type type_sal  is table of emp.emp %type index by binary_integer;

     l_ary_name  type_ename;

     l_ary_job    type_job;

     l_ary_sal    type_sal;

  Begin

     open myCur;

     loop

        fetch myCur bulk collect into 

        l_ary_name,  

        l_ary_job,   

        l_ary_sal

        limite 1;

        exit when myCur%notfound;

        dbms_output.put_line(myCur%rowCount||' '||l_ary_name(1)||' '||l_ary_job(1)||' '||l_ary_sal(1));

     end loop;

  End



  Declare

     Cursor myCur is select ename,job,sal from emp;

     type type_ename  is table of emp.ename %type index by binary_integer;

     type type_job  is table of emp.job %type index by binary_integer;

     type type_sal  is table of emp.emp %type index by binary_integer;

     l_ary_name  type_ename;

     l_ary_job    type_job;

     l_ary_sal    type_sal;

  Begin

     open myCur;

     loop

        fetch myCur bulk collect into 

        l_ary_name,  

        l_ary_job,   

        l_ary_sal

        limite 1;

        forall i in 1..l_ary_name.count

          insert into  table_b

          (b.name,b.job,b.sal)

         values(l_ary_name(i),l_ary_job(i),l_ary_sal(i))

        exit when myCur%notfound;



     end loop;

  End