选择插槽最大的行

Question

我需要选择slot_left最大的一行。我试过了

for ( $i=1;$i<3;$i++) {
    $sql5 = "SELECT * from user u where (
        select max(slot_left) from company c,user u 
        where c.id=u.company_id and c.id='$name'
    )";
    $result5 = mysqli_query($link, $sql5) or die(mysqli_error($link));
    while($row=mysqli_fetch_array($result5)) {  
        // echo the id which the slot_left is the biggest      
        echo $i['slot_left'];
    }
}

但仍然不能。请帮忙！

Answer 1

1. SQL可以。您从DB中选择所有行。

   $ sql5 =“select max（slot_left）AS slot_left from company c，user u where c.id = u.company_id and c.id ='$ name'GROUP by u.company_id”;

2. 查询中未使用的$ name变量

3. 变量$ i不是数组。数组是$ row

   echo $ row ['slot_left'];

Answer 2

您必须在查询中使用GROUP BY。 并且不建议在循环中执行查询，它会降低性能。

试试这个。

$sql5 = "select c.id, max(slot_left) from company c,user u 
        where c.id=u.company_id and c.id='$id' GROUP by c.id";

    $result5 = mysqli_query($link, $sql5) or die(mysqli_error($link));
    while($row=mysqli_fetch_array($result5)) {  
        echo $row['slot_left'];
    }