MYSQL如何在基于父表插入数据时用外键更新子表值

Question

I have 2 table, a parent table and child table. Child table has foreign key to parent table. I have successfully create the foreign key. But how to auto update field 'nama' based on parent table while I only insert 'id_parent' ? I only tried :

INSERT INTO child (id_parent) values (1)

but field 'name' value is still NULL

Here my tables :

CREATE TABLE `child` (
  `id` int(6) NOT NULL AUTO_INCREMENT,
  `id_parent` int(6) DEFAULT NULL,
  `nama` varchar(20) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `aa` (`nama`,`id_parent`),
  CONSTRAINT `aa` FOREIGN KEY (`nama`, `id_parent`) REFERENCES `parent` (`nama`, `id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=armscii8;

-- ----------------------------
-- Table structure for parent
-- ----------------------------
CREATE TABLE `parent` (
  `id` int(5) NOT NULL AUTO_INCREMENT,
  `nama` varchar(20) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `nama` (`nama`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=armscii8;

the parent table has data like this

INSERT INTO `parent` VALUES ('4', 'asa');
INSERT INTO `parent` VALUES ('1', 'batman');
INSERT INTO `parent` VALUES ('3', 'goku');
INSERT INTO `parent` VALUES ('2', 'robin');
INSERT INTO `parent` VALUES ('5', 'usu');

Answer 1

Check this line:

KEY `aa` (`nama`,`id_parent`),
  CONSTRAINT `aa` FOREIGN KEY (`nama`, `id_parent`) REFERENCES `parent` (`nama`, `id`)

here you have created a foreign key relationship on two column ie parent ( nama , id ). In that case you can only insert those combination values in child table that are already in parent table. Remember, here foreign key is implemented by combining two columns, not on a single column.

Answer 2

In my case I had a Location TransId column in my child table. I have update the location name from the parent ti child table column. I done with the below

UPDATE Table_A SET Table_A.CityName = Table_B.LocationDesc

from

<ParentTable> AS Table_A
INNER JOIN <ChildTable> AS Table_B
    ON Table_A.CityTransID = Table_B.TransID