php - mysql php从2个表中减去2个字段改进查询

Question

大家好，我正在尝试改进我的查询以获得更好的性能是否可以以更好的方式编写此查询，非常感谢您的帮助

$query = " SELECT A  FROM out_org where zone_id='1'";
$query2 = " SELECT A  FROM out_dis where zone_id='1'";

$result = mysql_query($query);
$result2 = mysql_query($query2);

echo "<table border=1 style='background-color:#F0F8FF;' >";
echo "<caption><EM>my table</EM></caption>";
echo "<tr>";
echo "<th>" .OA. "</th>" ;
echo "<th>" .DA. "</th>";
echo "<th>" .total. "</th>";
echo "</tr>";

while($row = mysql_fetch_array($result)  )
{
    while( $row2 = mysql_fetch_array($result2)){
        echo "<tr>";          
        echo "<td>" .$row['A']."</td>";
        echo "<td>" .$row2['A']."</td>";
        echo "<td>" .$total = $row['A'] - $row2['A']."</td>";         
        echo "</tr>";           
    }
    echo "</table>";
}

Answer 1

使用连接将您的 SQL 更改为一个查询，并在查询中进行减法：

$query = "SELECT (o1.A - o2.A) as value 
          FROM out_org o1 
               LEFT JOIN out_dis o2 
               ON o1.zone_id = o2.zone_id
           WHERE o1.zone_id='1'";