Question

I have two arrays with anywhere from 1 to 5 set values. I want to insert these values into a table with two columns.

Here’s my current query, given to me in another SO question:

INSERT INTO table_name (country, redirect) 
VALUES ('$country[1]', '$redirect[1]'), 
       ('$country[2]', '$redirect[2]'), 
       ('$country[3]', '$redirect[3]'),
       ('$country[4]', '$redirect[4]'),
       ('$country[5]', '$redirect[5]')
ON DUPLICATE KEY UPDATE redirect=VALUES(redirect)

I’m a little concerned however with what happens if some of these array values aren’t set, as I believe the above assumes there’s 5 sets of values (10 values in total), which definitely isn’t certain. If a value is null/0 does it automatically skip it?

Would something like this work better, would it be a lot more taxing on resources?

for($i = 0, $size = $sizeof($country); $i <= size; $i++) {
$query = "INSERT INTO table_name (country, redirect) VALUES ('$country[$i]', '$redirect[$i]) ON DUPLICATE KEY UPDATE redirect='$redirect[$i]'";
$result = mysql_query($query);
}

Questions highlighted in bold ;). Any answers would be very much appreciated 🙂 :)!!

Answer 1

Do something like this:

$vals = array()
foreach($country as $key => $country_val) {
    if (empty($country_val) || empty($redirect[$key])) {
       continue;
    }
    $vals[] = "('" . mysql_real_escape_string($country_val) . "','" . mysql_real_escape_string($redirect[$key]) . "')";
}
$val_string = implode(',', $vals);

$sql = "INSERT INTO .... VALUES $val_string";

That’ll built up the values section dynamically, skipping any that aren’t set. Note, however, that there is a length limit to mysql query strings, set by the max_allowed_packet setting. If you’re building a “huge” query, you’ll have to split it into multiple smaller ones if it exceeds this limit.