如何创建触发器来连接字段

how to create trigger to do concatenation of fields(如何创建触发器来连接字段)

问题描述

我有 1 个这样的表:

I have 1 table like this:

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

我想编写一个触发器，它将名字和姓氏连接到全名.

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

我试过下面的触发器:

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;
|

向用户表插入数据时出现此错误:

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

#1442 - 无法更新存储函数/触发器中的表用户"，因为它已被调用此存储函数/触发器的语句使用.

推荐答案

当 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 ;

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