Question

有两个表：'回复'和'帖子'，此触发器放在'回复'表中。

每次在回复表中放置一个新条目时，触发器会检查post表上一行中值是否为某些条件，且匹配的ID为新条目。

这是我到目前为止所做的：

CREATE TABLE posts(
p_Id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
p_Health INT UNSIGNED NOT NULL DEFAULT 0, 
p_Bump INT UNSIGNED NOT NULL DEFAULT 0,
p_Time TIMESTAMP);

CREATE TABLE replies(
r_Id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
r_To INT UNSIGNED NOT NULL,
r_Time TIMESTAMP);

CREATE TRIGGER bump AFTER INSERT ON replies
FOR EACH ROW
BEGIN
  IF posts.p_Bump < 5 WHERE posts.p_Id = NEW.r_To AND (SELECT COUNT(r_To) FROM replies WHERE r_To = NEW.r_To)%10 = 10 THEN
    UPDATE posts 
      SET posts.p_Bump = posts.p_Bump + 1 AND
      SET posts.p_Health = 0 WHERE posts.p_Id = NEW.r_To;
  END IF;
END;

INSERT INTO posts() VALUES();
INSERT INTO replies(r_To) VALUES(1);
INSERT INTO replies(r_To) VALUES(1);

INSERT INTO posts() VALUES();
INSERT INTO replies(r_To) VALUES(2);
INSERT INTO replies(r_To) VALUES(2);
INSERT INTO replies(r_To) VALUES(2);

'r_To'是“回复”的简写，它存储了回复所针对的帖子的ID。 SQLFiddle说第4行有一个错误，我尝试用SELECT COUNT(r_To)进行算术运算，模数为10。

无法创建SQLFiddle，如果它不正确，它不会保存我的架构。

Answer 1

这里有两个问题！首先，您需要更改分隔符以定义触发器。

DELIMITER $$
CREATE TRIGGER bump AFTER INSERT ON replies
FOR EACH ROW
BEGIN
  IF posts.p_Bump < 5 WHERE posts.p_Id = NEW.r_To AND (SELECT COUNT(r_To) FROM replies WHERE r_To = NEW.r_To)%10 = 10 THEN
    UPDATE posts 
      SET posts.p_Bump = posts.p_Bump + 1 AND
      SET posts.p_Health = 0 WHERE posts.p_Id = NEW.r_To;
  END IF;
END;

DELIMITER ;

第二个是sqlfiddle.com不支持delimiter命令，所以你不能用这种方式创建一个小提琴。我不知道sqlfiddle的工作，但在控制台中键入它应该可以解决问题。

不确定这是否合法

IF posts.p_Bump < 5 WHERE posts.p_Id = NEW.r_To AND (SELECT COUNT(r_To) FROM replies WHERE r_To = NEW.r_To)%10 = 10 THEN

我认为你必须这样做

SELECT COUNT(r_To) into @myvar FROM replies WHERE r_To = NEW.r_To;
IF @myvar %10 = 10 THEN
   UPDATE posts 
      SET posts.p_Bump = posts.p_Bump + 1 AND
      SET posts.p_Health = 0 WHERE posts.p_Bump < 5 AND  posts.p_Id = NEW.r_To;
END IF;

这是一个更简单的查询，我认为它符合您的期望。但是someint % 10永远不会是10，它只能取0到9的值，所以你必须为此提出正确的条件。

Answer 2

我认为模数应该在子选择

中完成

BEGIN
  IF posts.p_Bump < 5 
       WHERE posts.p_Id = NEW.r_To 
       AND (SELECT COUNT(r_To)%10 
              FROM replies WHERE r_To = NEW.r_To) = 10 THEN
    UPDATE posts 
      SET posts.p_Bump = posts.p_Bump + 1 AND
      SET posts.p_Health = 0 WHERE posts.p_Id = NEW.r_To;
  END IF;
END;

Mysql触发数学计算

2 个答案: