如果同时插入两条记录，如何获取最后一个 id

Question

I have a query, i have written a program in such a way an entry created in database and i am getting last_id, used this last id to update in second table.

$table='user';
$data = array('array having user data');
$this->db->insert($table, $data);
$last_id = $this->db->insert_id();

$this->db->where('user_id', $last_id);
$this->db->set('wallet_total_amount', "wallet_total_amount");

In such program when two entries created at exactly same time then the id of second transaction updated with first record. how to avoid this. please suggest.

Answer 1

You need to use transactions, basically committing one query after the other. Transactions allow you to perform one set of queries at a time, locking the database until all the queries are run (or rolled back, in case of errors).

User 1

auto commit off

1. Run query 1 (Insert data)
2. Retrieve last_insert_id
3. Run query 2 using last_insert_id

commit

User 2

auto commit off

1. Run query 1 (Insert data)
2. Retrieve last_insert_id
3. Run query 2 using last_insert_id

commit

To use transactions in codeigniter, have a look to this answer. Here you can find the PHP documentation.