Question

Im gonna try to explain what I need to do.

I have a table and in that table I have ID. This ID is my primary key (auto_increment).
And I have a second table.

What I need is when I save something in my seconds table I want to use the ID of my first table.

I have read much things but I only got more headache from it so if anyone could help me with this I would be gratefull.

Rgrds

Answer 1

You need the concept of a foreign key. This can be defined as a constraint or just used as such. Let’s assume you have “Teachers” and “Pupils” and pupils are assigned to one teacher. So the teacher has an ID. Now your “Pupils” table has an ID as well (it’s primary key) and a foreign key TEACHER_ID, which refers to the teacher entry.

ALTER TABLE `Pupils` ADD FOREIGN KEY (TEACHER_ID) REFERENCES `Teachers` (ID)

will create a constraint, that TEACHER_ID refers to the ID of a Teacher.

In PHP if you create both entries at once. You can first insert the teacher and then use:

$teacherID = mysql_insert_id();

which will return you the last auto_increment value (in this case your teachers ID) and then set this as the TEACHER_ID for your pupils entry.