我正在使用UNION从3个表中获取COUNT行。 但是似乎只收到一个结果。 并显示“未定义的偏移量1和2”

Question

When I run this my browser brings back a notice.. "Undefined offsets 1 and 2"

$sql = "SELECT COUNT(id) FROM new UNION
        SELECT COUNT(id) FROM whatshot UNION
        SELECT COUNT(id) FROM featured";

if($query = $db->query($sql))
{
    $row = $query->fetch_row();

    echo $row[0].' '.$row[1].' '.$row[2];
}

Answer 1

Your query will return three rows with one column each. You need to iterate fetch_row() .

|COUNT(id)|
===========
|    1337 |
|      23 |
|      42 |

Your code right now assumes one row with three columns.

Answer 2

you have not 3 column you get 3 rows (if the result is different in each row)

you should iterate over the result

    $sql = "SELECT COUNT(id) as my_count FROM new UNION
            SELECT COUNT(id) FROM whatshot UNION
            SELECT COUNT(id) FROM featured";

    if($query = $db->query($sql))
    {
        while($row = $query->fetch_row();

        echo $row['mycount'] . <br />;
    }

if you want always the 3 row use union all

$sql = "SELECT COUNT(id) as my_count FROM new UNION ALL
            SELECT COUNT(id) FROM whatshot UNION ALL 
            SELECT COUNT(id) FROM featured";

because union return only distinct result