plsql中游标使用

打开游标后的循环  

declare

  i_total integer:=1000;

  cursor emp_cur is select * from emp order by salary asc;

  i_emp emp%rowtype;

  begin

    open emp_cur;

    loop

      fetch emp_cur into i_emp;

      exit when emp_cur%notfound;

      i_total:=i_total+i_emp.salary;

      end loop;

     close emp_cur;

      dbms_output.put_line(i_total);

      end;
      select into 

create or replace procedure t_p(emp_id number) is

 v_name varchar2(1000);

begin

  select first_name into v_name from emp where employee_id=emp_id;

  dbms_output.put_line(v_name);

  end;

  

      动态查询

create or replace procedure p1(employee_id number, department_id number) is

      i_name varchar2(100);

      begin

        execute immediate 'select first_name from emp where employee_id='||employee_id ||' and department_id='||department_id into i_name;

        dbms_output.put_line(i_name);

        end;

动态查询，结果放到集合中

create or replace procedure p2(department_id number) is

  type names is table of varchar2(100);

  i_name names;

begin

  execute immediate 'select first_name from emp where department_id=' ||

                    department_id bulk collect

    into i_name;

  for idx in 1 .. i_name.count loop

    dbms_output.put_line(i_name(idx));

  end loop;

end;

游标变量

游标变量的使用范围

Pass a cursor variable back to the host environment that called the program unit—the result set can be “consumed” for display or other processing.

Construct a result set inside a function, and return a cursor variable to that set. This is especially handy when you need to use PL/SQL, in addition to SQL, to build the result set.

Pass a cursor variable to a pipelined table function—a powerful but quite advanced optimization technique. A full explanation of cursor variables, including the differences between strong and weak REF CURSOR types, is beyond the scope of this article.

Instead, I will show the basic syntax for working with cursor variables and identify situations in which you might consider using this feature

  CREATE OR REPLACE FUNCTION names_for(name_type_in IN VARCHAR2)

    RETURN SYS_REFCURSOR IS

    l_return SYS_REFCURSOR;

  BEGIN

    CASE name_type_in

      WHEN 'EMP' THEN

        OPEN l_return FOR

          SELECT last_name FROM emp ORDER BY employee_id;

      WHEN 'DEPT' THEN

        OPEN l_return FOR

          SELECT name FROM departments ORDER BY id;

    END CASE;

  

    RETURN l_return;

  END names_for;

使用游标变量

DECLARE

   l_names   SYS_REFCURSOR;

   l_name    VARCHAR2 (32767);

BEGIN

   l_names := names_for ('DEPT');

   LOOP

      FETCH l_names INTO l_name;

      EXIT WHEN l_names%NOTFOUND;

      DBMS_OUTPUT.put_line (l_name);

   END LOOP;

   CLOSE l_names;

END;

 

没有显示声明的游标是隐式游标，隐式游标有被称为sql游标，可以使用游标属性查看游标的信息。

  update emp
set email ='test'where employee_id =
123;
  dbms_output.put_line(sql%rowcount ||
'rows been updated');
  ifsql%notfoundthen
    dbms_output.put_line('no record');
  endif;
  commit;
exception
  whenothersthen
    dbms_output.put_line(SQLERRM);
end;
显示游标提供了比隐式游标更多的功能，通常使用显示游标处理select语句返回的多行数据。

在游标中指定参数

declare
  cursor emp_cursor(p_deptno
innumber)
is
    select *
from emp where deptno = p_deptno;
begin
  open emp_cursor(20);
end;
 

指定游标的返回类型

 
declare
  cursor emp_cursor(p_deptno
innumber)
return emp%rowtypeis
    select *
from emp wehre deptno = p_deptno;
begin
  open emp_cursor(20);
end;
使用bulk collect语句批量提取游标数据

declare
  type depttab_type
istableof dept%rowtype;
  depttab depttab_type;
  cursor deptcur
is
    select *
from dept;
begin
  open deptcur;
  fetch deptcur
bulkcollect
    into depttab;
  for i
in1 .. depttab.count
loop
    dbms_output.put_line(depttab(i)
                         .deptno ||
' ' || depttab(i).dname||
' ' || depttab(i).loc);
  endloop;
  close deptcur;
end;
 

使用bulk collect limit语句批量提取游标数据，用于游标中的数据量很大的情况下

 
declare
  type t9_type
isvarray(4)
of t9%rowtype;
  t9tab t9_type;
  cursor t9_cursor
is
    select *
from t9;
  v_rows  int :=
4;
  v_count int :=
0;
begin
  open t9_cursor;
  loop
    fetch t9_cursor
bulkcollect
      into t9tab
limit v_rows;
    exitwhen t9_cursor%notfound;
    dbms_output.put('名字');
    for i
in1 .. (t9_cursor%rowcount - v_count)
loop
     dbms_output.put(t9tab(i).object_name ||
' ');
    endloop;
    dbms_output.new_line;
    v_count := t9_cursor%rowcount;
    dbms_output.put_line(v_count);
  endloop;
  close t9_cursor;
end;

修改游标数据

declare
  cursor t9_cursor(p_id
innumber)
is
    select *
from t9 where object_id = p_id
forupdate;
begin
  for t9_row
in t9_cursor(20)
loop
    update t9
set object_name =
'test'wherecurrentof t9_cursor;
  endloop;
  commit;
end;
 

 

delete也是一样的

delete from t9 where current of t9_cursor;

 

之前声明的游标，在定义的时候就绑定了一个查询，这种的游标称为静态游标，游标变量是在定义的时候不绑定到具体的查询，可以打开任何类型兼容的查询。

declare
  type emp_type
isrefcursorreturn emp%rowtype;
  emp_cur emp_type;
  emp_row emp%rowtype;
begin
  open emp_cur
for
    select *
from emp;
  loop
    fetch emp_cur
      into emp_row;
    exitwhen emp_cur%notfound;
    dbms_output.put_line('name' || emp_row.ename);
  endloop;
end;
 

可以使用sys_refcursor类型的游标来定义游标变量下面的2个语句是等效的

Type emp_type is ref cursor;

Emp_cur emp_type;

与下面的语句是等效的

emp_cursor sys_refcursor;