Question

我有两个表Product（Productname VARCHAR（10），Rating REAL）和Review（RatingID INT，Productname VARCHAR（10），Rating INT）。产品的评级是该特定产品评论中给出的所有评级的平均值我希望有一个触发器，每当插入或更新新的评论时都会更新产品，但我无法理解如何做到这一点。是否有一些db2等同于SQL Server中的inserted（）？

我对这个微弱的问题道歉。

Answer 1

DB2 After Insert触发器：

CREATE TRIGGER NEW_REVIEW
 AFTER INSERT ON REVIEW
  REFERENCING NEW AS N_ROW
   FOR EACH ROW
    UPDATE PRODUCT SET Rating = (
      Select AVG(Rating) 
      from Review 
      where ProductName = N_ROW.ProductName
      )

更新后：

CREATE TRIGGER NEW_REVIEW
 AFTER UPDATE ON REVIEW
  REFERENCING NEW AS N_ROW
   FOR EACH ROW
    UPDATE PRODUCT SET Rating = (
      Select AVG(Rating) 
      from Review 
      where ProductName = N_ROW.ProductName
      )

删除后：

CREATE TRIGGER NEW_REVIEW
 AFTER DELETE ON REVIEW
  REFERENCING OLD AS O_ROW
   FOR EACH ROW
    UPDATE PRODUCT SET Rating = (
      Select AVG(Rating) 
      from Review 
      where ProductName = O_ROW.ProductName
      )

查看CREATE TRIGGER statement了解更多信息。

用于计算另一个表中的平均值的DB2 Trigger

1 个答案: