sql语句多条件查询

$sql = "SELECT * FROM 表名 WHERE 1=1";if($region!=null){     $sql .= " AND 字段='$region'";}

if($hold!=null){     $sql .= " AND 字段like '%$hold%' AND 字段<70 AND 字段between 100 and 150";}
$result = mysqli_query($conn,$sql);$output = [];while(true){    $row = mysqli_fetch_assoc($result);    if($row == null) break;    $output[] = $row;}echo(json_encode($output));