Question

I have a typical situation, where I need pull multiple rows from mysql by their ID’s. I only know two methods how to do so, but I’m wondering if there is a better way to do this? and if there isn’t, then which one of my own methods is most neatest/fastest/better?

My 1st method: (~0.0003030)

$ids = array(3, 4, 6, 11);

foreach ($ids as $id) {
    $task = $DB->query_first("SELECT * FROM tasks WHERE `id` = '$id'");
    DoSomethingWithTheTask($task);
}

My 2nd method: (~0.0001040)

$ids = array(3, 4, 6, 11);

foreach ($ids as $id) {
    $wheres[] = '`id` = \'' . $id . '\'';
}

$tasks = $DB->query("SELECT * FROM tasks WHERE " . implode(' OR ', $wheres));

while ($task = $DB->fetch_array($tasks)) {
    DoSomethingWithTheTask($task);
}

The reason why I’m even considering the second method, is because it uses only 1x query.. However, I strongly believe that both of these methods are not neat and need to be optimized. As far as I know, you cannot make a query like this: WHERE id = '2, 3, 4'.

Answer 1

Actually, you can. IN operator does that.

SELECT * FROM tasks WHERE `id` IN (2, 3, 4)

would do the trick. you can use both numeric or string values with IN operator

As Johan failed with example, here is a right way

$ids = array(3, 4, 6, 11);
$in  = implode(",",$ids);
$sql = "SELECT * FROM tasks WHERE `id` IN ($in)");

for the frequent use I’d make a placeholder, to call the whole expression this way

$ids  = array(3, 4, 6, 11);
$data = $db->getArr("SELECT * FROM tasks WHERE `id` IN (?a)",$ids);

to answer your questions from the comments, here is a code from my db class

function escapeString($value)
{
    return  "'".mysql_real_escape_string($value,$this->connect)."'";
}
function createIN($data)
{
    if (!is_array($data))
    {
        throw new E_DB_MySQL_parser("Value for ?a type placeholder should be array.");
    }
    if (!$data)
    {
        throw new E_DB_MySQL_parser("Empty array for ?a type placeholder.");
    }
    $query = $comma = '';
    foreach ($data as $key => $value)
    {
        $query .= $comma.$this->escapeString($value);
        $comma  = ",";
    }
    return $query;
}

getArr() method has no direct relation to this as it’s responsible for only type of result.