tables related with foreign key are synched with each other - mysql

Question

I am using phpmyadmin for mysql. I have 4 tables project1, project2, project3 and combine table. suppose combine table is connected to all other tables with the foreign keys and we add some data with the help of some background script to project1, prject2, and project3 tables. Is there any way to update the corresponding foreign keys in the combine table automatically ( without manually updating the record). I am using a yii framework for the GUI.
Please suggest some way as I am new to mysql and yii framework.

Answer 1

http://dev.mysql.com/doc/refman/5.6/en/create-table-foreign-keys.html
Not fully understanding your question but I think you are referring to ON DELETE and ON UPDATE.
ON DELETE & ON UPDATE options
CASCADE
SET NULL
NO ACTION
RESTRICT
ON DELETE & ON CASCADE are placed as constraints in the FK table and they occur when parent ID is either deleted or updated.
So if you change an id within the projects table and you wish for this change to be reflected in the combine table, you would use ON UPDATE CASCADE.
As a side note, why do you have 4 tables? I can only see the need for 2 tables.
Please note that SQL below may not be syntactically correct.
CREATE TABLE tbl_projects (
id integer NOT NULL PRIMARY KEY AUTO INCREMENT,
name varchar(255),
...
...
);
Method 1 creating a row for each project in the combine table:
CREATE TABLE tbl_combine (
id integer NOT NULL PRIMARY KEY AUTO INCREMENT,
project_id integer,
...
CONSTRAINT `FK_combine_project`
FOREIGN KEY (`project_id`)
REFERENCES `tbl_project` (`id`)
ON DELETE CASCADE ON UPDATE CASCADE
);
Method 2:
CREATE TABLE tbl_combine (
id integer NOT NULL PRIMARY KEY AUTO INCREMENT,
project1_id integer,
project2_id integer,
project3_id integer,
...
CONSTRAINT `FK_combine_project1`
FOREIGN KEY (`project1_id`)
REFERENCES `tbl_project` (`id`)
ON DELETE CASCADE ON UPDATE CASCADE
CONSTRAINT `FK_combine_project2`
FOREIGN KEY (`project2_id`)
REFERENCES `tbl_project` (`id`)
ON DELETE CASCADE ON UPDATE CASCADE
CONSTRAINT `FK_combine_project3`
FOREIGN KEY (`project3_id`)
REFERENCES `tbl_project` (`id`)
ON DELETE CASCADE ON UPDATE CASCADE
);
You can also do this via GUI in phpmyadmin by setting the foreign keys as an index by clicking a button, then going to the table relation view and choosing your options.
Hope this helps - I have attached an phpmyadmin image for you to see.