group by 的使用方法

数据库:

1.一个条件分组查询

$sql = "select brand,count(*),sum(price),avg(price),max(price),min(price) from goods group by brand";
$result = mysqli_query($link,$sql);
if(mysqli_num_rows($result)>0)
{
    while($row = mysqli_fetch_assoc($result))
    {
        echo '品牌有'.$row['brand'],'品牌的数量是'.$row['count(*)'].'价格的总和是'.$row['sum(price)'].' 平均值是'.$row['avg(price)'].'最大值是'.$row['max(price)']. '最小值是'.$row['min(price)'].'<br>';
    }
}
else
{
    echo '错误';
    exit;
}

 2.二个条件分组查询

//多条件分组group by
$sql = "select brand,pro_adds,count(*) from goods group by brand,pro_adds";
$result = mysqli_query($link,$sql);
if(mysqli_num_rows($result)>0)
{
   
    while($row = mysqli_fetch_assoc($result))
    {
        echo $row['brand'],$row['pro_adds'],$row['count(*)'].'<br>';
    }
}
else
{
    echo '错误';
    exit;
}