(mysql, php) How to get auto_increment field value before inserting data?

Question

I\'m uploading image file to storage server. Before uploading I should compose filename, which contains AUTOINCREMENT VALUE in it (for example, 12345_filename.jpg).

Answer 1

The autoincrement value is generated by the database itself, when the insertion is done ; which means you cannot get it before doing the actual insert query.

The solution you proposed is not the one that's often used -- which would be :

• insert some half-empty data
• get the autoincrement value that's been generated
• do your calculations, using that autoincrement value
• update the row to put the new / full data in place -- using the autoincrement generated earlier in the where clause of the update query, to identify which row is being updated.

Of course, as a security precaution, all these operations have to be made in a transaction (to ensure a "all or nothing" behavior)

As pseudo-code :

begin transaction
insert into your table (half empty values);
$id = get last autoincrement id
do calculations
update set data = full data where id = $id
commit transaction

Answer 2

Well this is to old ,but if someone else need it.

You can get this kind of value at "information_schema" table where you could do something like

select AUTO_INCREMENT from TABLES where TABLE_SCHEMA = 'You're Database' and TABLE_NAME = 'Table Name'

So this kind of Meta Data are always stored in Information_schema .