如何创建触发器以进行字段串联

Question

我有1张桌子，像这样：

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

我想编写一个将first_name和last_name连为full_name的触发器。

我已经尝试过以下触发器：

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;
|

在向用户表插入数据时显示此错误：

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

Answer 1

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。

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 ;