mysql - 查询未选择的最接近值

Question

我认为下面的代码中的这一行: Poscode , ABS( Poscode - :distance ) AS distance 被忽略:

所以它只是考虑这一行，因此返回所提供邮政编码的确切记录，而不是列出与给定邮政编码最接近的所有记录!

$bindings[] = array(":distance", $postcode, PDO::PARAM_STR);

查询:

$rate=$data['slider1'];

$key =array_keys($data['sub']); 
//print_r($key);
$pricing2 = $data['slider1'];
$pricing = $pricing2 * 1.15;
$postcode = $data['postcode'];


$bindings = array();
$bindings[] = array(":pricing", $pricing, PDO::PARAM_STR);
$bindings[] = array(":distance", $postcode, PDO::PARAM_STR);

$key_placeholders = array();
foreach($key as $k => $v) {
    $placeholder = ":subid".$k;
    $bindings[] = array($placeholder, $v, PDO::PARAM_INT);
    $key_placeholders[] = $placeholder;
}
$sql = "SELECT Name,PostUUID,pricing,Poscode , ABS( Poscode - :distance ) AS distance,subname,Reputation,ReviewPlus,ReviewNeg,week_morning,week_afternoon,week_evening,weekend_morning,week_afternoon,week_evening,weekend_morning,weekend_afternoon,week_evening,weekend_morning,weekend_afternoon,weekend_evening,date,Phone,Sex,UUID,catname FROM posts,subjects,categories "
        . "WHERE posts.subid IN (". implode(",",$key_placeholders).") "
        . "AND posts.pricing <=:pricing "
        . "AND posts.Poscode =:distance "
        . "AND posts.subid=subjects.subid "
        . "AND subjects.catid=categories.catid "
        . "ORDER BY distance "
        . "DESC LIMIT 100";

$statement = $pdo->prepare($sql);
foreach($bindings as $b) {
    $statement->bindValue($b[0],$b[1],$b[2]);
}
$statement->execute();

Answer 1

语句的 SELECT 部分选择为每行返回哪些数据 - 因此 ABS( Poscode - :distance ) AS distance 将返回一个名为 的字段distance 即每行的字段 Poscode 与值 :distance 之间的差。

语句的 WHERE 部分选择要返回的行。

因此，如果您想更改返回的行(以获取给定距离内的条目)，您需要更改 WHERE 子句。