Oracle游标

Posted 2021-02-17 小传风

语句语法忒复杂，眼花缭乱的记不住，放几个例子。

游标属性：

 Cursor_name%FOUND     布尔型属性，当最近一次提取游标操作FETCH成功则为 TRUE,否则为FALSE；

 Cursor_name%NOTFOUND   布尔型属性，与%FOUND相反；

 Cursor_name%ISOPEN     布尔型属性，当游标已打开时返回 TRUE；

 Cursor_name%ROWCOUNT   数字型属性，返回已从游标中读取的记录数。

显示游标：

无参游标：

DECLARE
  CURSOR c_cursor IS
    SELECT sname, sage FROM l_student_info_tbl WHERE rownum < 5;
  v_sname l_student_info_tbl.sname%TYPE;
  v_sage  l_student_info_tbl.sage%TYPE;
BEGIN
  OPEN c_cursor;
  FETCH c_cursor
    INTO v_sname, v_sage;
  WHILE c_cursor%FOUND LOOP
    DBMS_OUTPUT.PUT_LINE(v_sname || \'---\' || to_char(v_sage));
    FETCH c_cursor
      INTO v_sname, v_sage;
  END LOOP;
  CLOSE c_cursor;
END;

遍历也可以这样（个人比较喜欢下面fetch）：

DECLARE
  CURSOR c_cursor IS
    SELECT sname, sage FROM l_student_info_tbl WHERE rownum < 5;
  v_sname l_student_info_tbl.sname%TYPE;
  v_sage  l_student_info_tbl.sage%TYPE;
BEGIN
  OPEN c_cursor;
  LOOP
    FETCH c_cursor
      INTO v_sname, v_sage;
    EXIT WHEN c_cursor%NOTFOUND;
    DBMS_OUTPUT.PUT_LINE(v_sname || \'---\' || v_sage);
  END LOOP;
  CLOSE c_cursor;
END;

for 遍历更简洁（推荐）：

DECLARE
  CURSOR c_cursor IS
    SELECT sname, sage FROM l_student_info_tbl WHERE rownum < 5;
  --v_stu  c_cursor%rowtype;
BEGIN
  for v_stu in c_cursor loop
    DBMS_OUTPUT.PUT_LINE(v_stu.sname || \'---\' || v_stu.sage);
  end loop;
END;

还可以如下遍历：

DECLARE
  CURSOR c_cursor IS
    SELECT sname, sage FROM l_student_info_tbl WHERE rownum < 5;
  
  --定义数组
  type t_snage is table of l_student_info_tbl.sname%type;
  type t_sage is table of l_student_info_tbl.sage%type;

  v_arr_sname t_snage;
  v_arr_sage  t_snage;
BEGIN

  open c_cursor;
  fetch c_cursor bulk collect
    into v_arr_sname, v_arr_sage;
  close c_cursor;

  for i in v_arr_sname.first .. v_arr_sname.last loop
    dbms_output.put_line(v_arr_sname(i) || \'---\' || v_arr_sage(i));
  end loop;

END;

return子句：

DECLARE
  type stu_record_type is record(
    v_sname    l_student_info_tbl.sname%type,
    v_sage     l_student_info_tbl.sage%type,
    v_sgender  l_student_info_tbl.sgender%type,
    v_sclassno l_student_info_tbl.sclassno%type);

  v_stu_record stu_record_type;
  TYPE stu_cursor_type IS REF CURSOR RETURN stu_record_type;
  c1 stu_cursor_type;
BEGIN
  OPEN c1 FOR
    SELECT sname, sage, sgender, sclassno
      FROM l_student_info_tbl
     WHERE sage = 30;
  LOOP
    FETCH c1
      INTO v_stu_record;
    EXIT WHEN c1%NOTFOUND;
    DBMS_OUTPUT.PUT_LINE(\'名称：\' || v_stu_record.v_sname || \'  年龄：\' ||
                         v_stu_record.v_sage || \'  性别：\' ||
                         v_stu_record.v_sgender);
  END LOOP;
  CLOSE c1;
END;

 

有参游标：

DECLARE
  CURSOR c_cursor(v_limit_num number default 5) IS
    SELECT sname, sage FROM l_student_info_tbl WHERE rownum < v_limit_num;

BEGIN
  for v_stu in c_cursor(8) loop
    DBMS_OUTPUT.PUT_LINE(v_stu.sname || \'---\' || v_stu.sage);
  end loop;
END;

隐式游标

对于非查询语句，如修改、删除操作，则由ORACLE 系统自动地为这些操作设置游标并创建其工作区，这些由系统隐含创建的游标称为隐式游标，隐式游标的名字为SQL。

格式：SQL%

注：INSERT, UPDATE, DELETE, SELECT 语句中不必明确定义游标。

隐式游标属性

eg1：删除EMPLOYEES表中某部门的所有员工，如果该部门中已没有员工，则在DEPARTMENT表中删除该部门

DECLARE
  V_deptno department_id%TYPE := &p_deptno;
BEGIN
  DELETE FROM employees WHERE department_id = v_deptno;
  IF SQL%NOTFOUND THEN
    DELETE FROM departments WHERE department_id = v_deptno;
  END IF;
END;

eg2:通过隐式游标SQL的%ROWCOUNT属性来了解修改了多少行

DECLARE
  v_rows NUMBER;
BEGIN
  --更新数据
  UPDATE employees
     SET salary = 30000
   WHERE department_id = 90
     AND job_id = \'AD_VP\';
  --获取默认游标的属性值
  v_rows := SQL%ROWCOUNT;
  DBMS_OUTPUT.PUT_LINE(\'更新了\' || v_rows || \'个雇员的工资\');
  --回退更新，以便使数据库的数据保持原样
  ROLLBACK;
END;