这个SQL IF语句有什么问题？

Question

so I am building a search script and meed to pass on two variables, but first I want to make sure that the SQL QUery is correct so I am hard-coding the variable for now. So my variable is

$comma_separated = "'Alberta','Ontario'";

This is getting passed through to the query, which looks like this:

$sql = "SELECT * FROM persons WHERE 1=1";



if ($firstname)
$sql .= " AND firstname='" . mysqli_real_escape_string($mysqli,$firstname) . "'";

if ($surname)
$sql .= " AND surname='" . mysqli_real_escape_string($mysqli,$surname) . "'";

if ($province)
$sql .= " AND province='" . mysqli_real_escape_string($mysqli,$comma_separated) . "' WHERE province IN ($comma_separated)";

$sql .= " ORDER BY surname";

and then when the query runs, I get this message:

cannot run the query because: You have an error in your SQL syntax; check the manual that    corresponds to your MySQL server version for the right syntax to use near 'WHERE province IN ('Alberta','Ontario') ORDER BY surname LIMIT 0, 5' at line 1

But to me the query looks right, what am I missing here?

Thanks in advance.

Answer 1

You can't have WHERE in there twice. You also seem to be trying to filter on province values in two different ways. Based on the assumption that $province will always be an array of values (even if only a single value is given), you can try this:

$sql = "SELECT * FROM persons WHERE 1=1";

if (!empty($firstname)) {
    $sql .= " AND firstname='" . mysqli_real_escape_string($mysqli,$firstname) . "'";
}

if (!empty($surname)) {
    $sql .= " AND surname='" . mysqli_real_escape_string($mysqli,$surname) . "'";
}

if (!empty($province)) {
    array_walk($province, function($value, $key_not_used) use ($mysqli) {
        return mysqli_real_escape_string($mysqli, $value);
    });
    $sql .= " AND province IN ('" . implode(',', $province) . "')";
}

$sql .= " ORDER BY surname";