查询未正确排序

Question

我正在使用这个查询。我需要按 $variis 对其进行排序，但排序似乎不起作用。我仔细检查了字段名称和表格。一切都是正确的，但它不会按 $variis 对其进行排序：

代码：

//Unseen
$variis = "Need Help";
$myid = This is the user's id;

$sql = "select car_help.car_id, agent_names.agent_name, help_box.status, 
car_help.why_car, car_help.date_time_added, car_help.just_date, 
car_help.type, agent_names.agent_id
from car_help LEFT JOIN agent_names on car_help.agent_whois = agent_names.agent_id 
where agent_names.system_id = '$myid' and car_help.system_id='$myid' 
and added_by <> '$myid' and help_box.status = '$variis'
UNION
select magazine_help.note_id, agent_names.agent_name, help_box.status, 
magazine_help.note_name, magazine_help.date_time_added, 
magazine_help.just_date, magazine_help.type, agent_names.agent_id
from magazine_help LEFT JOIN agent_names on 
magazine_help.agent_id = agent_names.agent_id 
where agent_names.system_id='$myid' and 
magazine_help.system_id = '$myid' and added_by <> '$myid' 
and help_box.status = '$variis'
UNION
select motorcycle_help.rand_id, agent_names.agent_name, 
help_box.status, motorcycle_help.rand_name, motorcycle_help.date_time_added,     
motorcycle_help.just_date, motorcycle_help.type, agent_names.agent_id
from motorcycle_help LEFT JOIN agent_names ON 
motorcycle_help.by_who = agent_names.agent_id
where agent_names.system_id = '$myid' and 
motorcycle_help.system_id='$myid' and added_by <> '$myid' 
and help_box.status = '$variis'
UNION
select mobile_questions.bal_test_id, agent_names.agent_name, 
help_box.status, mobile_questions.bal_why, mobile_questions.date_time_added,   
mobile_questions.just_date, mobile_questions.type, agent_names.agent_id
from mobile_questions LEFT JOIN agent_names ON 
mobile_questions.agent_who_ordered = agent_names.agent_id
where agent_names.system_id = '$myid' and 
mobile_questions.system_id='$myid' and added_by <> '$myid' 
and help_box.status = '$variis'
ORDER BY date_time_added DESC LIMIT $startrow, 20";

$result = mysql_query($sql);

$query = mysql_query($sql) or die ("Error: ".mysql_error());


if ($result == "")
{
echo "";
}
echo "";


$rows = mysql_num_rows($result);

if($rows == 0)
{
print("");

}
elseif($rows > 0)
{
while($row = mysql_fetch_array($query))
{

$row1 = $row['row_name'];


print("$row1");
}

}

好的更新：我选择了 status 字段并显示了它。对于返回的所有这些行，状态为不需要帮助，而 $variis 实际上是需要帮助

Answer 1

请阅读手册： http://dev.mysql.com/doc/ refman/5.1/en/union.html

要使用 ORDER BY 或 LIMIT 子句对整个 UNION 结果进行排序或限制，请将各个 SELECT 语句放在括号内，并将 ORDER BY 或 LIMIT 放在最后一个语句之后。以下示例使用这两个子句：

(SELECT a FROM t1 WHERE a=10 AND B=1)
UNION
(SELECT a FROM t2 WHERE a=11 AND B=2)
ORDER BY a LIMIT 10;

Answer 2

试试这个：

from magazine_help LEFT JOIN agent_names on 
magazine_help.agent_id = agent_names.agent_id **and help_box.status = '$variis'**
where agent_names.system_id='$myid' and 
magazine_help.system_id = '$myid' and added_by <> '$myid' 

不要在 where 子句中使用 *and help_box.status = '$variis'* ，而是在连接中使用它

Answer 3

我相信“排序”是指“过滤”。
每次在 WHERE 子句中需要 help_box.status 时，都应该在 FROM 子句中包含 help_box 表。只有这样它才能运行。