php - 显示mysqli查询的单列值

Question

如何从 mysqli 获取单个列值？结果应该是单行只有一列。

这是我尝试过的:

$query = "SELECT MAX(`userid`) FROM `user`";
$rlt = mysqli_query($this->db, $query);
echo $rlt['userid'];

Answer 1

执行查询后您没有获取行:

$query = "SELECT MAX(`userid`) FROM `user'";
$rlt = mysqli_query($this->db,$query);
$row = mysqli_fetch_row($this->db, $rlt);
echo $row[0];

另一种方法是使用计算字段的别名并使用fetch_assoc:

$query = "SELECT MAX(`userid`) as `maxid` FROM `user'";
$rlt = mysqli_query($this->db,$query);
$row = mysqli_fetch_assoc($this->db, $rlt);
echo $row['maxid'];