MySQL workbench - self referring table and custom script - mysql

Question

I use MySQL 5.3.28 to create my database. One of the tables is referring itself, which is a big pain. Here is the originally created code:
CREATE TABLE IF NOT EXISTS `dhbpsychiatry`.`activity` (
`ActivityId` INT(11) NOT NULL AUTO_INCREMENT ,
`NeedsRepeating` BINARY(1) NULL DEFAULT NULL ,
`Prerequisition` INT(11) NOT NULL DEFAULT 0 ,
`ActivityName` VARCHAR(45) NOT NULL ,
`ActivityDescription` VARCHAR(45) NULL ,
PRIMARY KEY (`ActivityId`) ,
INDEX `Prerequisition` (`ActivityId` ASC) ,
CONSTRAINT `Prerequisition`
FOREIGN KEY (`ActivityId` )
REFERENCES `dhbpsychiatry`.`activity` (`ActivityId` )
ON DELETE NO ACTION
ON UPDATE NO ACTION)
Problem is of course with creating first row.
INSERT INTO `dhbpsychiatry`.`activity` (`ActivityId`, `Prerequisition`,
`ActivityName`) VALUES (1, 1, 'No prerequisition');
returns
ERROR 1452: Cannot add or update a child row: a foreign key constraint fails
Same if I try even simpler
INSERT INTO `dhbpsychiatry`.`activity` (`ActivityName`)
VALUES ('No prerequisition');
I think I've tried all possibilities, making the FK nullable, not nullable, with or without default value...
After digging a bit I've found something that works:
SET FOREIGN_KEY_CHECKS = 0;
Insert into activity (ActivityID, ActivityName) VALUES (0,'No prerequisition');
SET FOREIGN_KEY_CHECKS = 1;
So I created a new SQL script in workbench with those lines.
So I have two questions here:
How I can add the first row without the script?
or if its impossible
2 How can I automatically add this script to be executed whenever I froward engineer the database?

Answer 1

Your indexes and Foreign key definitions are confused. Main issue is that column ActivityId is referencing itself.
Try this:
CREATE TABLE IF NOT EXISTS `dhbpsychiatry`.`activity` (
`ActivityId` INT(11) NOT NULL AUTO_INCREMENT ,
`NeedsRepeating` BINARY(1) NULL DEFAULT NULL ,
`Prerequisition` INT(11) NOT NULL DEFAULT 0 ,
`ActivityName` VARCHAR(45) NOT NULL ,
`ActivityDescription` VARCHAR(45) NULL ,
PRIMARY KEY (`ActivityId`) ,
INDEX `Prerequisition_idx` (`Prerequisition`) , --- changed the index name
--- and the indexed column
CONSTRAINT `Prerequisition_fk` --- changed the constraint name
FOREIGN KEY (`Prerequisition` ) --- main issue !! changed
--- the referencing column
REFERENCES `dhbpsychiatry`.`activity` (`ActivityId`)
ON DELETE NO ACTION
ON UPDATE NO ACTION
)