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

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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

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