如何创建触发器以进行字段串联 [英] how to create trigger to do concatenation of fields

问题描述

我有1张这样的桌子:

user
----------------------------------------
id | first_name | last_name | full_name
----------------------------------------

我想编写一个触发器，以将名字和姓氏连接成全名.

I want to write a trigger which will concat the first_name and last_name to full_name.

我尝试了以下触发器:

delimiter |
create trigger fullname after insert on user
for each row
begin
update user set full_name=(select concat(first_name,last_name) from user where id=new.id)where id=new.id;
end;
|

在向用户表中插入数据时显示此错误:

It's shows this error while inserting data to user table:

#1442 - Can't update table 'user' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.

推荐答案

在INSERT触发器触发时，您无法更改表.但是，您可以在插入记录之前创建触发器.

You cannot change a table while the INSERT trigger is firing. You can, however, create a trigger before inserting the record.

DELIMITER |
CREATE TRIGGER `fullname` BEFORE INSERT ON `user`
FOR EACH ROW 
BEGIN
  SET NEW.full_name = CONCAT(NEW.first_name, ' ', NEW.last_name);
END |
DELIMITER ;

这篇关于如何创建触发器以进行字段串联的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！