php - MySql ORDER By rand() 一行

Question

我有这个 php 代码

$coma_count=substr_count($Hob,',');
        if ($coma_count==0) {
            $query="SELECT * FROM user_opt WHERE Interests='$Hob' LIMIT 80";
        }else{
            $expl=explode(',',$Hob);
            for ($i=0; $i <=$coma_count; $i++) { 
                    $query.=" UNION SELECT * FROM users WHERE Interests LIKE '%{$expl[$i]}%'";      
            }
}
    $sql=$con->query($query." ORDER BY RAND()") or die($con->error);

$coma_count 的数量从 0 到 112 不等，问题是当 $coma_count 为 0 时(意味着仅选择了国家/地区)，我的查询将如下所示SQL 不接受 SELECT * FROM user_opt WHERE Country='$Countr' LIMIT 80 ORDER BY RAND()。我能做什么？

Answer 1

创建一个 $limit 变量，根据需要设置它，然后附加它:

$limit = '';
$coma_count=substr_count($Hob,',');
    if ($coma_count==0) {
        $query="SELECT * FROM user_opt WHERE Interests='$Hob'";
        $limit = " LIMIT 80";
    }else{
        $expl=explode(',',$Hob);
        for ($i=0; $i <=$coma_count; $i++) { 
                $query.=" UNION SELECT * FROM users WHERE Interests LIKE '%{$expl[$i]}%'";      
        }
}
$sql=$con->query($query." ORDER BY RAND()".$limit) or die($con->error);