檢查表中是否存在值 - 觸發器

Question

我正在嘗試編寫觸發器來控制記錄是否已在表中。如果記錄已在表中（例如按名稱比較），那麼當前記錄集合valid ='False'並插入新記錄。有什麼辦法嗎？

這是我的想法，但它不起作用。

create or replace TRIGGER 
Check_r 
    before insert on t$customer 
    FOR each ROW 
    declare 
    v_dup number; 
    v_com number; 
    v_id number; 
    v_id_new number; 
    begin 
    v_date:=SYSDATE; 
     select count(id) INTO v_dup from t$customer where surname=:NEW.surname ; 
     select count(id) INTO v_com from t$customer where firstname =:NEW.firstname and 
     address=:NEW.address; 
     select id into v_id from t$customer where surname=:NEW.surname; 
    if v_dup > 0 and v_com=0 then 
    v_id_new:= m$_GET_ID; -- get id 
    update t$customer set valid = 'False' where id = v_id; 
    insert into t$customer (id, surname ,firstname, valid, address) values (v_id_new,:NEW.surname ,:NEW.firstname, :NEW.valid, :NEW.address); 
    end if; 
    if v_dup = 0 then 
    v_id_new:= m$_GET_ID; -- get id 
    insert into t$customer (id, surname ,firstname, valid , address) values (v_id_new,:NEW.surname ,:NEW.firstname, :NEW.valid, :NEW.address); 
    end if; 
    end; 

Answer 1

首先，這是插入的觸發器。你不需要編寫插入語句。

其次，您需要更新舊記錄。只需使用where子句進行更新即可。

CREATE OR REPLACE TRIGGER Check_r 
before insert on t$customer 
FOR each ROW 
BEGIN 
    UPDATE t$customer set valid = 'False' 
    WHERE surname = :NEW.surname 
    AND firstname =:NEW.firstname; 
:NEW.id := m$_GET_ID; 
END; 

Answer 2

您可以使用複合觸發器，例如：

CREATE OR REPLACE TRIGGER Check_r 
    FOR INSERT ON t$customer 
    COMPOUND TRIGGER 

    TYPE customerRecordType IS RECORD(
     surname t$customer.surname%TYPE, 
     firstname t$customer.firstname%TYPE, 
     address t$customer.address%TYPE, 
     ID nubmer); 
    TYPE customerTableType IS TABLE OF customerRecordType; 
    customerTable customerTableType := customerTableType(); 

    n NUMBER; 

BEFORE STATEMENT IS 
BEGIN  
    customerTable.DELETE; -- not requried, just for better understanding 
END STATEMENT; 


BEFORE EACH ROW IS 
BEGIN  
    customerTable.EXTEND; 
    customerTable(customerTable.LAST).surname := :NEW.surname; 
    customerTable(customerTable.LAST).firstname := :NEW.firstname; 
    customerTable(customerTable.LAST).address := :NEW.address; 
    customerTable(customerTable.LAST).ID := m$_GET_ID; 
    :NEW.ID := customerTable(customerTable.LAST).ID; 
END BEFORE EACH ROW; 

AFTER STATEMENT IS 
BEGIN 
    FOR i IN customerTable.FIRST..customerTable.LAST LOOP  
     SELECT COUNT(*) INTO n 
     FROM t$customer 
     WHERE surname = customerTable(i).surname;  
     IF n > 1 THEN 
      UPDATE t$customer 
      SET valid = 'False' 
      WHERE surname = customerTable(i).surname; 
     END IF; 

     SELECT COUNT(*) INTO n 
     FROM t$customer 
     WHERE firstname = customerTable(i).firstname 
      AND address = customerTable(i).address; 
     IF n > 1 THEN 
      UPDATE t$customer 
      SET valid = 'False' 
      WHERE firstname = customerTable(i).firstname 
       AND address = customerTable(i).address 
     END IF; 
    END LOOP; 

END AFTER STATEMENT;  

END; 
/

請注意，這個解決方案是醜陋和貧窮方面的性能！ 但它應該給你一個印象它是如何工作的。

一般來說，你應該把所有這些放到PL/SQL過程而不是觸發器中。