mySQL bind_param与IN(？)

Question

使用bind_param我的所有查询,我现在想要使用IN(?)列表中元素数量可以变化的位置.

我在这里使用基本SQLOUT功能做了$sql_db->prepare,->bind_param,->execute(),->store_result(),->bind_result

// the code below does not work as the query only matches on element 'a':
$locations = ('a','b','c','d','e');

SQLout ("SELECT Name FROM Users WHERE Locations IN (?)",
    array('s', $locations), array(&$usrName));


// the code below does work as a brute-force method,
// but is not a viable solution as I can't anticipate the number of elements in $locations going forward:

SQLout ("SELECT Name FROM Users WHERE Locations IN (?,?,?,?,?)",
    array('sssss', $locations[0],$locations[1],$locations[2],$locations[3],$locations[4]), array(&$usrName));

有没有人想出更优雅的解决方案呢？

Answer 1

这是一个占位符落在他们脸上的地方.减去自动转义,它们几乎只是内部的字符串替换操作,这意味着如果你有WHERE Locations IN (?),并且传入1,2,3,4,你将得到相当于

WHERE Locations IN ('1,2,3,4')  // note, it's a string, not individual comma-separated integers

在逻辑上相当于

WHERE Locations = '1,2,3,4' // again, just a string

而不是更多的预期

WHERE Locations = 1 OR Locations = 2 OR Locations = 3 OR Locations = 4

唯一可行的解​​决方案是建立自己的列表?,例如:

$placeholders = implode(',', array_fill(0, count($values), '?'));
$sql = "SELECT Name FROM Users WHERE Locations IN ($placeholders)";

然后绑定你的参数是很平常的.