最大數量計算錯誤

Question

patient_id：1,2,3,4,5,6,7,8,9,10

 $result2=mysql_query("select max(patient_id) as maximum from outdoor");
        $row2= mysql_fetch_array($result2);
      echo $res=$row2['maximum'];

它的最大數量為9而不是10。

Answer 1

嘗試這個

$sql = "select max(CONVERT(patient_id,UNSIGNED INTEGER)) as maximum from outdoor";

Answer 2

用這個

$sql = "select GREATEST(patient_id) as maximum from outdoor";

使用GREATEST（）

例如：

SELECT GREATEST(2,1);