mysql> USE mydb;
Database changed
mysql> INSERT INTO t(c1) VALUES(123);
ERROR 1364 (HY000): Field 'c2' doesn't have a default value
mysql>

-- MySQL Script generated by MySQL Workbench
-- 02/21/17 08:26:27
-- Model: New Model    Version: 1.0
SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0;
SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0;
SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='TRADITIONAL,ALLOW_INVALID_DATES';

-- -----------------------------------------------------
-- Schema mydb
-- -----------------------------------------------------
DROP SCHEMA IF EXISTS `mydb` ;
CREATE SCHEMA IF NOT EXISTS `mydb` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci ;
USE `mydb` ;

-- -----------------------------------------------------
-- Table `mydb`.`t`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `mydb`.`t` (
  `c1` INT NOT NULL AUTO_INCREMENT,
  `c2` INT NOT NULL,
  PRIMARY KEY (`c1`))
ENGINE = InnoDB;


SET SQL_MODE=@OLD_SQL_MODE;
SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS;
SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS;
USE `mydb`;

DELIMITER $$
USE `mydb`$$
CREATE TRIGGER `t_BINS` BEFORE INSERT ON `t` FOR EACH ROW
begin
SET NEW.c2=321;
end$$


DELIMITER ;