插入之前MySQL触发

Question

I cant get this to work, it runs OK, but nothing happens in insert

DROP TRIGGER IF EXISTS test;
DELIMITER $$
CREATE
    TRIGGER test BEFORE INSERT 
    ON prueba 
    FOR EACH ROW     
    BEGIN
        SET NEW.jo=1
    END
DELIMITER $$;
insert into prueba (ja) values (16);

CREATE TABLE `prueba` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `ja` int(11) DEFAULT NULL,
  `jo` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

LOCK TABLES `prueba` WRITE;

What im i doing wrong??

Answer 1

if I have understood correct then what you are actually trying to achieve is to have a default value of 1 for the column jo . in such case no need of a before insert trigger . You can just define that as default value for that column while creating the table like

CREATE TABLE `prueba` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `ja` int(11) DEFAULT NULL,
  `jo` int(11) DEFAULT 1, <-- Notice This Line
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Then after insertion, you will have a record as

ID  JA  JO
1   16  1

See a demo Fiddle Here

Talking about your create trigger syntax. Try the below modified trigger code

DELIMITER $$
CREATE TRIGGER test BEFORE INSERT ON prueba 
    FOR EACH ROW  
    BEGIN   
        SET NEW.jo=1;
    END$$
DELIMITER ;