Question

有人知道我的触发器声明有什么问题吗？

CREATE TRIGGER `sch_trigger_curriculum_subject_before_insert` BEFORE INSERT ON  
`sch_curriculum_subject` FOR EACH ROW 
BEGIN
   DECLARE curriculum_code VARCHAR(50);        
   SET curriculum_code = SELECT code FROM sch_curriculum WHERE id=NEW.id;
   SET NEW.`code_name` = CONCAT(curriculum_code,' - ', NEW.code,' - (',NEW.name,')');
END;

错误：SQL错误（1064）：您的SQL语法错误.....在第4行附近。

根据错误消息，我的curriculum_code声明有问题。但我不知道出了什么问题。

提前致谢

更新已经解决，问题是分隔符，这是工作的

DELIMITER $$
CREATE TRIGGER `sch_trigger_curriculum_subject_before_insert` BEFORE INSERT ON  
`sch_curriculum_subject` FOR EACH ROW 
BEGIN
  DECLARE curriculum_code VARCHAR(50);        
  SET curriculum_code = (SELECT code FROM sch_curriculum WHERE id=NEW.id);
  SET NEW.`code_name` = CONCAT(curriculum_code,' - ', NEW.code,' - (',NEW.name,')');
END$$

Answer 1

您不能以这种方式为变量分配SELECT语句。至少你应该将SELECT语句放在括号中以将其作为子查询执行，但更好的是：

SELECT code FROM sch_curriculum WHERE id = NEW.id INTO curriculum_code;

请注意，查询不会返回多条记录（假设UNIQUE列中存在id约束，因此这可能不是问题。）

Answer 2

您需要确保不会从SELECT返回多个值。

尝试：

SET curriculum_code = (SELECT code FROM sch_curriculum WHERE id=NEW.id LIMIT 1);

Answer 3

你不能简单地SET curriculum_code = some_SQL。我怀疑你的意思是SELECT ... INTO curriculum_code

MySQL在触发错误中声明变量

3 个答案: