解决当distinct和join同时存在distinct失效问题

请看下面的例句：

$sql = 'select distinct(ontopid),gb.id as id,f.id as fid,g.id as
gid,g.*,gb.*,f.* from pk_groupbuy gb

left join pk_ontop as o on
o.ontopid=gb.id

left join pk_goods g on
gb.goodsid=g.id and g.status=2 and g.invalid>UNIX_TIMESTAMP()

left join pk_fastgroupbuy f on
gb.fastgroupbuyid=f.id

where gb.id in
('.$arr_str.') and (gb.status="2" or gb.status="3")

and
gb.endtime>UNIX_TIMESTAMP() and
gb.starttime<UNIX_TIMESTAMP()

group by onid limit
$start,$num";

return TableSystem::query($sql);

变量说明：$arr_str是一个由pk_groupbuy中主键 id组成的一个数组，经过explode函数得到的字符串，

$start,$num分别是查询的开始记录数，和要查询的记录数。

问题说明：pk_ontop表中ontopid在不能记录中有重复现象

比如：我只需要查询出来pk_ontop中当天置顶的ontopid，即商品id，不需要其他的商品信息，查询出来的有ontopid就算有重复现象，这时我可以通过去除数组重复元素解决问题，但是如果我要查询出相应商品id并查询其他相关联表中的信息，并按照ontop表中starttime，status，paixu字段进行排序等操作时，就需要join
pk_ontop表，所以之前解决的重复问题就又会出现，无法处理，特别是在api中，是不允许出现重复的，这要怎么办呢？我也不会额，别人教我这样弄，请大家参考下：

$sql = 'SELECT DISTINCT(ontopid),starttime,paixu FROM
pk_ontop ORDER BY starttime DESC,STATUS ASC,paixu ASC LIMIT
17';
$arr =
TableSystem::query($sql);
foreach($arr as
$key=>$val){
$topids[$key] =
$val['ontopid'];
}
$arr_str
= implode(',',$topids);
$arr1 =
TableSystem::query($sql);

$sql = 'select gb.local,f.phone,f.shopname as
fshopname,gb.maxnum,gb.intro,gb.buynum,g.pic,f.googleaddress,gb.goodsclassid,gb.sellerid,f.img,gb.province,gb.city,gb.id,gb.title,g.pic,gb.starttime,
gb.endtime,gb.price,gb.goodsprice
from pk_groupbuy gb
left join
pk_goods g on gb.goodsid=g.id and g.status=2 and g.invalid >
UNIX_TIMESTAMP()
left JOIN
pk_fastgroupbuy f ON
f.id=gb.fastgroupbuyid
where
(gb.status="2" or gb.status="3") and gb.endtime >
UNIX_TIMESTAMP()
and gb.starttime <
UNIX_TIMESTAMP() AND gb.id in
('.$arr_str.')';

$arr2 =
TableSystem::query($sql);
foreach($arr2 as
$key=>$val){
$local[$val['id']] =
$val['local'];
$phone[$val['id']] =
$val['phone'];
$fshopname[$val['id']] =
$val['fshopname'];
$maxnum[$val['id']] =
$val['maxnum'];
$intro[$val['id']] =
$val['intro'];
$buynums[$val['id']] =
$val['buynum'];
$fgoogleaddresss[$val['id']] =
$val['googleaddress'];
$goodsclassid[$val['id']]
= $val['goodsclassid'];
$sellids[$val['id']] =
$val['sellerid'];
$provices[$val['id']] =
$val['province'];
$citys[$val['id']] =
$val['city'];
$titles[$val['id']]=
$val['title'];
$pics[$val['id']] = $val['pic']
? $val['pic'] :
$val['img'];
$starttimes[$val['id']] =
$val['starttime'];
$endtimes[$val['id']] =
$val['endtime'];
$prices[$val['id']] =
$val['price'];
$goodsprices[$val['id']] =
$val['goodsprice'];
}
unset($arr2);
foreach($arr1
as $key=>$val){
$list[$key]['id'] =
$val['ontopid'];
$list[$key]['province'] =
$provices[$val['ontopid']];
$list[$key]['city']
= $citys[$val['ontopid']];
$list[$key]['title']
= $titles[$val['ontopid']];
$list[$key]['pic']
=
$pics[$val['ontopid']];
$list[$key]['starttime']
=
$starttimes[$val['ontopid']];
$list[$key]['endtime']
=
$endtimes[$val['ontopid']];
$list[$key]['price']
=
$prices[$val['ontopid']];
$list[$key]['goodsprice']
=
$goodsprices[$val['ontopid']];
$list[$key]['sellerid']
=
$sellids[$val['ontopid']];
$list[$key]['fgoogleaddress']
=
$fgoogleaddresss[$val['ontopid']];
$list[$key]['goodsclassid']
=
$goodsclassid[$val['ontopid']];
$list[$key]['buynum']
=
$buynums[$val['ontopid']];
$list[$key]['intro']
=
$intro[$val['ontopid']];
$list[$key]['maxnum']
=
$maxnum[$val['ontopid']];
$list[$key]['fshopname']
=
$fshopname[$val['ontopid']];
$list[$key]['fphone']
= $phone[$val['ontopid']];
$list[$key]['local']
=
$local[$val['ontopid']];
}
return
$list;