mySQL: index table of 2 other table ID's - php

Question

Ok, here's what I wanna do.
Table1(globalID [primary key, autoincremented] (is a global id i would use in PHP))
Table2 & table3(ID* [foreign primary key, referencing to globalID], other columns after this, different for each of the tables 2 and 3);
What I wannt to know is if there is a way, and how, to make it so that when I insert a row in table2 or table3 the globalID in talbe1 gets populated and it's value also inserted in table2 or table3 accordingly as an ID. I assume it would be accomplished with a trigger, but triggers are not my forte so if that's the only way it can be done please provide an example.
I was also thinking of expanding it to this scenario:
Table1(globalID [primary key, autoincremented] (is a global id i would use in PHP),
OtherID [an UUID]);
Table2 & table3(ID* [foreign primary key, referencing to OtherID], other columns after this, different for each of the tables 2 and 3);
But in that case there is still the almost nonexistent possibility that 2 users might generate the same UUID while inserting a new row in some table. I was wondering if i could avoid that by making the keys generated by the sql server automatically without me having to code it PHP server side.
If anyone has had this problem worked out and can also point out other things i need to watch out for or take into account please point them out. Also please provide an example of the solution.
EDIT:
#John B.
EDIT BY TosheX
thank you for the reply. I have been reading up on this in the meantime and i already have a solution outside of SQL (in php). Basically I use Yii PHP framework in which I create a model of the table, and create an active record to populate a new row. now when I do that the ID in table1 is generated, and afterwards I still have a variable that points to that populated row and I can just read the generated ID since it's automatically fetched (without having to check for the last record in the database, which may return the record someone created milliseconds after me). Afterwards I just need to create a row inside the appropriate table2 or 3 and assign the already generated value for the ID.
i found the idea here:
http://www.yiiframework.com/forum/index.php/topic/14593-alternate-for-mysql-insert-id/
I really wanted an inbuilt solution in the database, but since I have experience with databases and do know enough about triggers (enough to not like them :D ) i know it's a very tricky code to get right so I was wondering if there are alternatives to auto-populate or something.
Still, I really appreciate your response, since you took your time and all. I have been working in msSQL more too, and I find logic in what you said. UUID in mySQL is the same as GUID in msSQL and I have considered that too as you can see.
Taking all this into account I will go with the solution i found, but I will accept your answer since you did try to help out, and you did bring some good ideas to the table.
Thanks again.

Answer 1

I'm a mssql person, but I dont think it is possible, unless you can create a "BEFORE INSERT" trigger for your db (and even then it will be problematic), because:
Whatever the ID of Tables 2 & 3 is, be it an integer or a guid, these are primary keys: Being a primary key, this column will not allow nulls, yet what you require is essentially to create new rows in these tables, with this column null, and then generate a new row in Table1, and use the new value in that table to update the new row in either Table2 or Table3.
Therefore, you'll probably need to either:
Do a solution in code (ie outside of SQL) whereby you cause the creation of a new row in Table1 first, then use this value when subsequently creating in Table2/3, or:
On tables2/3 have a autoincremented column for your primary key lets call it "PK", then have ID as a separate ordinary FK but which allows nulls, plus a trigger as follows (though you might need to fiddle with the syntax a little bit, because I am a mssql person, and I don't know your db's syntax) :-(
Also this example is designed to work with a multiple row insert, and to achieve this uses a cursor, and my syntax for cursors is dodgy at best even in mssql!
CREATE TRIGGER trg_Table2 ON dbo.Table2
FOR INSERT /* might be AFTER INSERT etc */
AS BEGIN
SET nocount on;
Declare ICursor Scroll For SELECT PK FROM Inserted;
Declare #PK int,
#GlobalID int,
#ID guid;
OPEN ICursor
FETCH Next From ICursor INTO #PK
WHILE ##Fetch_Status BEGIN
INSERT Table1 (OtherID) VALUES (NewID());
SELECT #GlobalID = ##Identity
SELECT #ID = OtherID FROM Table1 WHERE GlobalID = #GlobalID
UPDATE Table2 SET ID = #ID WHERE PK = #PK
FETCH Next FROM ICursor INTO #PK
END
Close ICursor
Deallocate ICursor
END
Hope this helps