mysql - MySQL 多查询 - 构建额外的 SQL 参数

Question

我有以下代码：

$query  .= "SELECT COUNT( ". $r ." ) AS Total, 
(SELECT COUNT( ". $r ." ) FROM  tresults WHERE ". $r ." >=750) AS Eng, 
(SELECT COUNT( ". $r ." ) FROM  tresults WHERE ". $r ." >=450 AND ". $r ." <=749) AS Pas, 
(SELECT COUNT( ". $r ." ) FROM  tresults WHERE ". $r ." <=449) AS Dis
FROM  tresults;";

这是一个多重查询，使用 PHP 我可以查看多个实例并拉回数据——这很好。

但是，我需要做的是根据用户从下拉菜单中输入的内容轻松地向 SQL 查询添加其他参数。

因此，例如，用户可能会从下拉列表中选择一个选项，然后需要将其附加到 SQL 查询中，例如：

$query  .= "SELECT COUNT( ". $r ." ) AS Total, 
(SELECT COUNT( ". $r ." ) FROM  tresults WHERE ". $r ." >=750 AND q16 = 'Yes') AS Eng, 
(SELECT COUNT( ". $r ." ) FROM  tresults WHERE ". $r ." >=450 AND ". $r ." <=749 AND q16 = 'Yes') AS Pass, 
(SELECT COUNT( ". $r ." ) FROM  tresults WHERE ". $r ." <=449 AND q16 = 'Yes') AS Dis
FROM  tresults WHERE q16 = 'Yes';";

可能有一个附加，如上所述，或多个。

我以前没有尝试过这样的事情，所以我想知道在我深入研究之前是否有人有任何建议？

Answer 1

这是我的一般方法：

$filter = "AND q16 = 'Yes'"; //This value is dynamic depending on dropdown selection
$query  .= "SELECT COUNT( ". $r ." ) AS Total, 
(SELECT COUNT( ". $r ." ) FROM  tresults WHERE ". $r ." >=750 " . $filter ." ) AS Eng, 
(SELECT COUNT( ". $r ." ) FROM  tresults WHERE ". $r ." >=450 AND ". $r ." <=749 " . $filter ." ) AS Pass, 
(SELECT COUNT( ". $r ." ) FROM  tresults WHERE ". $r ." <=449 " . $filter ." ) AS Dis
FROM  tresults WHERE 1=1 " . $filter ." ;";