Question

我需要从表中获取max indentity值并将序列设置为该值。

为此，我试图在此触发器中读取表中的最大缩进值（触发当前触发器）并将序列设置为该值但是当我去阅读桌子时，我得到了变异的错误。我正在使用Oracle 11g。

所以我的问题是有没有办法在这个触发器中将序列值设置为表的max indentity值？请指教。

这是我的触发器;

create or replace
TRIGGER StringTextTrg BEFORE INSERT ON StringText
FOR EACH ROW
DECLARE 
v_newVal NUMBER(12) := 0;
v_incval NUMBER(12) := 0;
BEGIN
 IF INSERTING AND :new.STxtID IS NULL THEN
 SELECT  StringText_STxtID_SEQ.NEXTVAL INTO v_newVal FROM DUAL;
 -- If this is the first time this table have been inserted into (sequence == 1)
 IF v_newVal = 1 THEN 
  --get the max indentity value from the table
  SELECT NVL(max(STxtID),0) INTO v_newVal FROM StringText;
  v_newVal := v_newVal + 1;
  --set the sequence to that value
  LOOP
       EXIT WHEN v_incval>=v_newVal;
       SELECT StringText_STxtID_SEQ.nextval INTO v_incval FROM dual;
  END LOOP;
  END IF;
 -- assign the value from the sequence to emulate the identity column
 :new.STxtID := v_newVal;
 END IF;
END;

Answer 1

以下是我的回答，使用哪个是我强烈反对的：

CREATE OR REPLACE TRIGGER StringTextTrg
    BEFORE INSERT
    ON StringText
    FOR EACH ROW
DECLARE
    v_newVal   NUMBER (12) := 0;
    v_incval   NUMBER (12) := 0;
BEGIN
    IF INSERTING AND :new.STxtID IS NULL THEN
        SELECT StringText_STxtID_SEQ.NEXTVAL INTO v_newVal FROM DUAL;

        -- If this is the first time this table have been inserted into (sequence == 1)
        IF v_newVal = 1 THEN
            --get the max indentity value from the table
            SELECT NVL (MAX (STxtID), 0) INTO v_newVal FROM StringText;

            v_newVal := v_newVal + 1;

            --set the sequence to that value
            EXECUTE IMMEDIATE ('DROP SEQUENCE StringText_STxtID_SEQ');
            EXECUTE IMMEDIATE ('CREATE SEQUENCE StringText_STxtID_SEQ START WITH '||to_char(v_newVal));
        END IF;

        -- assign the value from the sequence to emulate the identity column
        :new.STxtID := v_newVal;
    END IF;
END;
/

序列是数据库对象。您无法重置它们，您必须删除并重新创建它们。因此，您必须（ab）为此作业使用动态SQL。

这不是创建自动生成的顺序整数主键列值的最佳做法。此外，请考虑禁止本栏目的手动条目，因为这些条目肯定会按照您尝试维护的顺序造成混乱。

Oracle - 将序列值设置为触发器中表的最大indentity值

1 个答案: