mysql_num_rows返回1

Question

为什么下面的代码返回1，尽管字段group_members中没有元素？

$conn = mysql_connect($host,$user,$pass);

@mysql_select_db($db);

$sql = "
    SELECT 
        group_members
    FROM
        tbl_group
    WHERE
        group_id = '6'      
";

$res = mysql_query($sql);

$rows = mysql_num_rows($res);

echo $rows;

＆GT;

Answer 1

您编写的SQL将选择group_id = 6的所有行，然后返回字段group_members的值，而不管内容如何。要获得所需内容，请尝试：

SELECT group_members FROM tbl_group WHERE group_id = 6 AND group_members <> '' // Depending on type might also be <> NULL or <> 0

Answer 2

您在tbl_group where group_id = '6'中存储了1条记录。

Answer 3

您可以在搜索标签中的phpmyadmin中搜索group_id = 6。您可以在group_id中查看6个。

Answer 4

使用phpmyadmin检查，组ID = 6的行数。