Oracle cursor的用法.

锁表,可以用来锁定表的数据.代码如下

DECLARE

  CURSOR lock_r IS

    SELECT *

      FROM cmx_if_invadj_detail t

     WHERE t.group_id = 1493

       FOR UPDATE NOWAIT;

BEGIN

  OPEN lock_r;

  CLOSE lock_r;

  dbms_output.put_line(11111);

EXCEPTION

  WHEN OTHERS THEN  --不需要再次关闭,因为cursor在open中已经raise了.

    dbms_output.put_line(22222);

END;

判断cursor是否为空,其实用法与exit用法一样,不过是不进行循环,直接判断.

DECLARE

  l_exists VARCHAR2(1);

  CURSOR lock_r IS

    SELECT 'X'

      FROM cmx_if_invadj_detail t

     WHERE t.group_id = 1492

       FOR UPDATE NOWAIT;

BEGIN

  OPEN lock_r;

  FETCH lock_r

    INTO l_exists;

  IF lock_r%NOTFOUND THEN

    dbms_output.put_line(11111);

  END IF;

  CLOSE lock_r;

EXCEPTION

  WHEN OTHERS THEN

    dbms_output.put_line(SQLERRM);

END;