Question

下面的代码只给我18条记录

<?php

$result4 = mysql_query("select Distinct Country  from trendsmtable where WHORegionAC='Europe - all countries' GROUP BY Country ");

echo "<table width=880 align=center>";
echo "<tr><td colspan=4 style='font-family:Arial;'><b>European Region</b></td></tr>";
$num_columns4 = 4;
$num_rows4 = mysql_num_rows($result4);
$i=0;
while($row4 = mysql_fetch_assoc($result4)){
    $results[$i] = $row4['Country'];
    $i++;
}
unset($i);
$k=0;
for ($i=0;$i<=($num_rows4/($num_columns4+1));$i++){
    echo '<tr>';

    for($j=1;$j<=$num_columns4;$j++){
        echo "<td width=220 style='font-family:Arial; font-size:12px'>".$results[$k].'</td>';
        $k++;
    }

    echo '</tr>';
$k++;
}
echo "</table>";

?>

而select语句

从trendmtable中选择Distinct Country WHORegionAC ='Europe - 所有国家的

返回22行，而我在mysql中执行它是正确的！

请帮我找到错误。

Answer 1

嗯，你有一个额外的$ k ++，你不需要：

        $k++; // keep this one
    }

    echo '</tr>';
    $k++; // remove this one
}

修改

我已经完成了你的代码并且我做了一些编辑。希望他们一路上能清理你的问题：

// got rid of group by. With a select distinct, it isn't necessary
$result4 = mysql_query("select Distinct Country  from trendsmtable where ".
                       "WHORegionAC='Europe - all countries'");

// a good practice is to always double-quote your HTML attributes.
echo "<table width=\"880\" align=\"center\">";
echo "<tr><td colspan=4 style=\"font-family:Arial;\">".
          "<b>European Region</b></td></tr>";

$num_columns4 = 4; // where does 4 come from.
// $results was never initialized before.
$results = array();
while($row4 = mysql_fetch_assoc($result4)){
    // This is generally thought of as "cleaner" than using an index. 
    // And since there cannot be more than, say, 220 rows, cleanliness
    // should be a high-priority standard.
    $results[] = $row4['Country'];
}

// mysql_num_rows rarely provides any major benefit at all.
$num_rows4 = count($results);

foreach( $results as $key => $val )
{
    // This happens every time we fill all columns and need a new row.
    if( !( $key % $num_columns4 ) ) 
    {
        // makes it so that after the first time this closes the prev 
        // row before starting a new one.
        if( $key ) echo '</tr>'; 
        echo '<tr>';
    }
    // insert nag about CSS
    echo '<td width="220" style="font-family:Arial; font-size:12px">'.
              $val.
         '</td>';
}
echo '</tr></table>';

Answer 2

我认为PHP看起来有点奇怪，看起来你正在从0循环到（22/5）然后在内循环中4次。

group by

时，select distinct不应该有任何区别

Answer 3

PHP文件中的SQL代码包含GROUP BY子句，如果数据库中有多个国家/地区，则可以减少返回的行数。

mysql查询在for循环中给出错误的结果

3 个答案:

修改