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[英]Select data from a MySQL table where some results from another table depends on a condition, if there are any
[英]Select from table where some WHERE condition missing
我有以下SQL请求
if(isset($_GET['room'])) {
if($_GET['status'] == 'all' && $_GET['room'] == 'all'){
$stmt = $pdo->prepare("SELECT DISTINCT flatnetto FROM flat ORDER BY flatnetto");
$stmt->execute(array($_GET['room'], $_GET['status']));
}else if($_GET['status'] == 'all'){
$stmt = $pdo->prepare("SELECT DISTINCT flatnetto FROM flat WHERE kk = ? ORDER BY flatnetto");
$stmt->execute(array($_GET['room']));
}else if($_GET['room'] == 'all'){
$stmt = $pdo->prepare("SELECT DISTINCT flatnetto FROM flat WHERE sold = ? ORDER BY flatnetto");
$stmt->execute(array($_GET['status']));
}else{
$stmt = $pdo->prepare("SELECT DISTINCT flatnetto FROM flat WHERE kk = ? AND sold = ? ORDER BY flatnetto");
$stmt->execute(array($_GET['room'], $_GET['status']));
}
$rows = $stmt->fetchAll(PDO::FETCH_ASSOC);
}
可以从上面的代码中仅发出一个sql请求吗? 我的意思是,可以只提出一个请求
$stmt = $pdo->prepare("SELECT DISTINCT flatnetto FROM flat WHERE kk = ? AND sold = ? ORDER BY flatnetto");
但条件“ kk”和“出售”可能存在或可能不存在(将具有无法分类的“全部”值)。 因此,例如,如果“ kk”不存在,则将其忽略,然后仅在条件为“卖出”的情况下继续选择。
上面的代码可以正常工作,但是定义所有可能的选项很烦人。
状态可以有值(已售,保留,全部)
房间可以有值(1kk,2kk,3kk,全部)
值“全部”意味着,例如,我在2kk会议室很有趣,无论是“出售”还是“保留”,都只向我展示它们。
更新的问题。
正如在下面的答案中所写,可以发出一个sql请求。 但是问题仍然存在,因为我们只是将“可能的选项定义”移至sql查询,但是我仍然必须定义所有可能的选项。 我无法想象如何定义所有可能的选项,如果我们不仅有两个输入,而且例如“房间,状态,price1,price2,地板,大小...”,并且它们都可以具有自己的价值,但还价值“全部” ”。 在这种情况下,我们必须从所有可能的变化中定义所有可能的选项(在这种情况下,超过20个可能的变化)。 我认为这在大型项目中是行不通的。
考虑所有可能性的联合查询。 根据选择参数,将仅输出一行查询:
$stmt = $pdo->prepare("SELECT DISTINCT flatnetto FROM flat WHERE kk = :kk
AND sold = :sold AND NOT kk = 'all' AND NOT sold = 'all ORDER BY flatnetto
UNION SELECT DISTINCT flatnetto FROM flat WHERE kk = 'all' AND sold = :sold
ORDER BY flatnetto
UNION SELECT DISTINCT flatnetto FROM flat WHERE kk = :kk AND sold = 'all'
ORDER BY flatnetto
UNION SELECT DISTINCT flatnetto FROM flat WHERE kk = 'all' AND sold = 'all'
ORDER BY flatnetto");
$stmt->execute(array(':kk' => $_GET['room'], ':sold' => $_GET['status']));
您可以使用以下代码来生成您的SQL查询
$param=Array();
## associate query parameters to sql column
$keys=Array("room" => "kk", "status" => "sold");
## generate parameter list
foreach ($keys as $k=>$v)
if (isset($_GET[$k])&&($_GET[$k]!='all'))
$param[$v]=$_GET[$k];
## generate query
$query="SELECT DISTINCT flatnetto FROM flat WHERE ".
implode(" = ? AND ", array_keys($param)).
(count($param) ? " = ?" : "1")
." ORDER BY flatnetto";
## execute
$stmt = $pdo->prepare($query);
$stmt->execute($param);
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