AUTO_INCREMENT MYsql?!

Hello,
I have a table in a database which handles products’ data. This table have many columns, two of them are the problem. The first one is [i]

product_id[/i] column and the second is [i]barcode[/i] column. On the application side, the user has the choice to make the barcode for the

product equals to the product_id value or not. The [i]product_id[/i] column is the primary key and it is [b]Auto Incremented[/b]. The [i]

barcode[/i] column is integer.
The problem is:
When I want to make the value [i]barcode[/i] column equals to the value of [i]product_id[/i] as follows,

[code]
INSERT INTO products (product_id, barcode) VALUES (“”,product_id);
[/code]

The value assigned to the [i]barcode[/i] = 0. This may due to that the primary key is an index and it is processed at later step of the query

after the [i]barcode[/i].
However, I used [b]mysql_insert_id()[/b] to get the last value of the auto_increment field, then by UPDATE clause I assign the value I want

to the barcode, [i]i.e barcode value = product_id value[/i]
The real problem is:
In a real world web application, I think, [b]mysql_insert_id()[/b] may return a wrong value or 0, this due to many users and clients

probably using the application at the same time, i.e the same table ([i]products[/i]). The manual of MySQL tell us the follwoing fact:-

[QUOTE]

The most recently generated ID is maintained in the server on a per-connection basis. It will not be changed by [b]another client[/b]. It will not

even be changed if you update another AUTO_INCREMENT column with a non-magic value (that is, a value that is not NULL and not 0).

[/QUOTE]

The question is : Is everyone (every web page’s browser to the application) using the web application regarded as single client? Or the

application itself (Website or PHP parser) regrded as the client?
If the answer to the second question is yes, what would I can to do to complete my task.
Best Regards.

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