mysql_insert_id（）可以从另一个脚本的查询中获取值

Question

The manual for mysql_insert_id() says

Because mysql_insert_id() acts on the last performed query, be sure to call mysql_insert_id() immediately after the query that generates the value.

This statement does not indicate any scope. Is it a serverwide value? Could a server running many scripts or many instances of one script return a value for mysql_insert_id() which was not generated by the last insert performed by the script calling it?

Answer 1

The scope of mysql_insert_id() is the MySQL connexion. Not the user + password, but the actual connection for the current script. (Note that the MySQL connection can also be a parameter of mysql_insert_id)

If you close and re-open the MySQL connexion, mysql_insert_id() will not return the id of the id inserted in the previous one.

If an id has been inserted just after your adding, but by another script execution (I mean with another connexion) the mysql_insert_id() will return your ID, not the ID actually created after your but in another connection.

Example :

$c1 = mysql_connect($srv, $usr, $pwd);
$c2 = mysql_connect($srv, $usr, $pwd);

$sql = "INSERT INTO table1 (col1, col2) VALUES('x', 'y') "
mysql_query($sql, $c1); // first insert
mysql_query($sql, $c2); // second insert

$id1 = mysql_insert_id($c1);
$id2 = mysql_insert_id($c2);

$id1 will be the id inserted first, $id2 the id inserted after.