Question

我正在尝试创建一个MySQL触发器，但无法正确获取语法。

触发器应该通过并匹配一组关键字与插入数据库的新帖子的标题。如果找到匹配项，则应将新帖子分配给该存储桶并更新存储桶关键字集。如果找不到匹配项，则应使用帖子中的值创建新的存储桶。错误指向以IF EXISTS开头的行，但我无法弄清楚出了什么问题。任何帮助将不胜感激。谢谢！

更新：代码已更新以提取IF EXISTS，但现在我从ELSE语句开始收到错误。

delimiter $$

CREATE TRIGGER bucket_trigger_v1 BEFORE INSERT ON posts
FOR EACH ROW
  BEGIN
    set @target = NEW.post_title;
    set @bucket_id_number = '';
    set @bucket_relevance = '';

    SELECT idbuckets, MATCH (keywords) AGAINST (@target) AS score INTO @bucket_id_number, @bucket_relevance FROM buckets WHERE MATCH (keywords) AGAINST (@target) ORDER BY score DESC LIMIT 1;
    IF (@bucket_id_number != '') THEN
      BEGIN
        SET NEW.buckets_idbuckets = @bucket_id_number;
        UPDATE buckets SET keywords = concat(keywords, @target) WHERE idbuckets = @bucket_id_number;
      END
      ELSE
      BEGIN
        INSERT INTO buckets (idbuckets, keywords, creationdate) VALUES (, @target, NEW.postdate);
        SET NEW.bucket_idbuckets = (SELECT LAST_INSERT_ID());
      END
    END IF;
END;

$$

Answer 1

要考虑的几点：

13.2.9.1. SELECT ... INTO Syntax

不应在嵌套的SELECT中使用INTO子句，因为这样 SELECT必须将其结果返回到外部上下文。

19.3.1. Trigger Syntax and Examples

这样的SET语句在AFTER触发器中没有效果，因为行已经发生了变化。

<强>更新

以下代码正确创建了触发器。仅创建posts表才能创建触发器。

/*Table structure for table `posts` */

DROP TABLE IF EXISTS `posts`;

CREATE TABLE `posts` (
  `post_title` VARCHAR(500) DEFAULT NULL,
  `buckets_idbuckets` INT(11) DEFAULT NULL,
  `postdate` DATETIME DEFAULT NULL
) ENGINE=INNODB;

/* Trigger structure for table `posts` */

DELIMITER $$

/*!50003 DROP TRIGGER*/ /*!50032 IF EXISTS */ /*!50003 `bucket_trigger_v1` */$$

CREATE TRIGGER `bucket_trigger_v1` BEFORE INSERT ON `posts`
FOR EACH ROW
BEGIN
    SET @target := new.`post_title`;
    SET @bucket_id_number := '';
    SET @bucket_relevance := '';
    SELECT `idbuckets`, MATCH (`keywords`) AGAINST (@target) AS `score` INTO @bucket_id_number, @bucket_relevance FROM `buckets` WHERE MATCH (`keywords`) AGAINST (@target) ORDER BY `score` DESC LIMIT 1;
    IF (@bucket_id_number != '') THEN
        SET new.`buckets_idbuckets` := @bucket_id_number;
        UPDATE `buckets` SET `keywords` = CONCAT(`keywords`, @target) WHERE `idbuckets` = @bucket_id_number;
    ELSE
        INSERT INTO `buckets` (`keywords`, `creationdate`) VALUES (@target, new.`postdate`);
        SET new.`buckets_idbuckets` := LAST_INSERT_ID();
    END IF;
END$$

DELIMITER ;

Answer 2

MySQL，或者至少我正在运行的版本，无法一次处理多个触发器。由于这个原因，IF语句不适用于BEGIN和END，所以我必须找到不同的解决方案。

存在MySQL触发器语法错误

2 个答案: