使用单个触发器更新多个表

Question

我在用一个触发器更新 2 个表时遇到问题，它在“New.userid”附近给我一个错误

CREATE TRIGGER userDownloads AFTER INSERT ON Downloads
FOR EACH ROW
UPDATE Project SET PROJECT_DOWNLOADS = PROJECT_DOWNLOADS + 1 WHERE PROJECTID = NEW.ProjectID,
UPDATE User SET NO_OF_DOWNLOADS = NO_OF_DOWNLOADS + 1 WHERE USERID = NEW.UserID;

Answer 1

你必须这样写你的触发器：

DELIMITER //
CREATE TRIGGER userDownloads AFTER INSERT ON Downloads
FOR EACH ROW
BEGIN
  UPDATE Project SET PROJECT_DOWNLOADS = PROJECT_DOWNLOADS + 1 WHERE PROJECTID = NEW.ProjectID;
  UPDATE User SET NO_OF_DOWNLOADS = NO_OF_DOWNLOADS + 1 WHERE USERID = NEW.UserID;
END//

请看here.

但是你确定你需要一个触发器吗？你为什么不在你的 Downloads 表上做一个 COUNT 呢？

SELECT ProjectID, COUNT(*) AS PROJECT_DOWNLOADS
FROM Downloads
GROUP BY ProjectID;

SELECT UserID, COUNT(*) AS NO_OF_DOWNLOADS
FROM Downloads
GROUP BY UserID;