Oracle PL / SQL中的游標

Question

我正在嘗試編寫一個游標以在Oracle中完成任務。 我對Oracle中的游標不熟悉。 顯然，我在這方面做錯了。 有人可以告訴我這是什么嗎？

DECLARE 
    CURSOR c1 IS
        SELECT BADGE.EMPID
        FROM EVENTS
        INNER JOIN BADGE ON EVENTS.CARDNUM = BADGE.ID
        INNER JOIN EMP ON BADGE.EMPID = EMP.ID
        WHERE EMP.VISITOR = 0
        AND EVENTS.EVENT_TIME_UTC - 0.125 > TO_DATE('20090101 00:00:00', 'RRRRMMDD hh24:mi:ss')
        AND EVENTS.EVENT_TIME_UTC - 0.125 < TO_DATE('20120101 23:59:59', 'RRRRMMDD hh24:mi:ss');
    r1 c1%ROWTYPE;
BEGIN
    FOR r1 IN c1 LOOP
    UPDATE EVENTS
    SET EVENTS.EMPID = r1.EMPID
    END LOOP;
END;  

謝謝你的幫助！

Answer 1

還有一種無需游標即可執行此操作的方法，但這就是您想要執行的操作。 關鍵是要定義光標，然后沿光標循環。 識別FOR UPDATE

DECLARE 
  CURSOR c1 IS
    SELECT BADGE.EMPID
    FROM EVENTS
    INNER JOIN BADGE ON EVENTS.CARDNUM = BADGE.ID
    INNER JOIN EMP ON BADGE.EMPID = EMP.ID
    WHERE EMP.VISITOR = 0
    AND EVENTS.EVENT_TIME_UTC - 0.125 > TO_DATE('20090101 00:00:00', 'RRRRMMDD hh24:mi:ss')
    AND EVENTS.EVENT_TIME_UTC - 0.125 < TO_DATE('20120101 23:59:59', 'RRRRMMDD hh24:mi:ss')
    FOR UPDATE of events.empid;
BEGIN
  for l in c1 loop 
    UPDATE events
      SET empid = l.empid
      WHERE CURRENT OF c1;
  end loop;
  COMMIT;
end;

Answer 2

不使用隱式游標的解決方案（無鎖定問題）：

Begin
  For X in (
        SELECT BADGE.EMPID, EVENTS.CARDNUM FROM EVENTS
        INNER JOIN BADGE ON EVENTS.CARDNUM = BADGE.ID
        INNER JOIN EMP ON BADGE.EMPID = EMP.ID
        WHERE EMP.VISITOR = 0 AND 
              EVENTS.EVENT_TIME_UTC - 0.125 > TO_DATE('20090101 00:00:00', 'RRRRMMDD hh24:mi:ss') AND 
              EVENTS.EVENT_TIME_UTC - 0.125 < TO_DATE('20120101 23:59:59', 'RRRRMMDD hh24:mi:ss')
    )
  Loop
    UPDATE EVENTS
    SET EVENTS.EMPID = X.EMPID
    WHERE EVENTS.CARDNUM = X.CARDNUM;
  END LOOP;
  COMMIT;
END;