how extract last auto_increment value?

Fermat

I've got two tables, one with some data and a user_id field, the other with a password field and user_id field. The user_id in table 1 is on auto_increment. The data and password come from a form. I insert the data into the 1st table with something like,

insert into table1 (user_id, var1, var2,...) values (null, $var1, $var2,...);

Now I've got to extract the value of user_id from table 1 so that I can insert the user's password along with the right user_id.
Can I use MAX(user_id)? Will that always return the last auto_incremented value of user_id?

I'm assuming that any two rows may be identical except for user_id, so I can't use a comparison of field values to extract a particular user_id value.

[edit]
p.s. how do I get the value of MAX() in php? I've got,

// get the unique vendor ref number, and save it.
$sql="select MAX(vend_id) from vendor";
$result=mysql_query($sql) OR DIE (mysql_error());
echo ("Num records = ".$result."<br>");

I get $result=resource id#3
How can I get $result=3?
[/edit]

jimson

I get $result=resource id#3
How can I get $result=3?

to get number of rows in mysql u need

mysql_num_rows(the resource//in ur case $result);

the show the result, u need mysql_fetch_array();
then print_r

please read the mysql functions in php manual.. there is explanation code there... download the manual if u haven't got one... please...

Fermat

Sorry, my fault. The last line of that code shoould have read,

echo ("MAX value of vend_id = ".$result."<br>");

The max value of vend_id actually was 3.

stick_figure

You need to get an array from the result set. Look at the functions in the previous post. Logically, if you had a result set with more than one row or column, how would you get that data following your method?

Fermat

ok, thanks, I got the value of MAX, I think, like this

// get the unique vendor ref number, and save it.
$sql="select MAX(vend_id) from vendor";
$result=mysql_query($sql) OR DIE (mysql_error());
$row=mysql_fetch_row($result);
$vend_id=$row['0'];
echo ("MAX value of vend_id = ".$vend_id."<br>");

and since $vend_id gives the right value each time, I assume the method is correct.

So now I've got the value of MAX, but going back to my original question,

If I use MAX(vend_id), will that always return the last auto_incremented value of vend_id?

Since I'm getting the right answer, and no-one's said otherwise. I'll assume that it does.

Thanks all.

ahundiak

Nope. Nope. Nope.

Use mysql_insert_id() to get newly inserted id.
http://www.php.net/manual/en/function.mysql-insert-id.php

Consider what happens if two people create a user record at about the same time. MAX could return the id for the other person's record. mysql_insert_id is connection based and will always give the correct result.

Fermat

Thanks. That's what I was after.