php - 是否可以在 MYSQL AND "clause"中使用 IF ELSE

Question

我下面的示例“显然”不起作用::: 有没有办法获得 IF ELSE 或类似的工作::: 我有几个 PHP 变量，基于这些变量我想更改此查询中的 AND“子句”，而不必创建多个查询并使用 PHP if 语句来使用正确的查询 block :::

$query = "SELECT $wpdb->posts.ID
          FROM $wpdb->posts 
          INNER JOIN $wpdb->postmeta ON ($wpdb->posts.ID = $wpdb->postmeta.post_id)
          WHERE 1=1 
          AND $wpdb->posts.post_type = 'cars' 
          AND ($wpdb->posts.post_status = 'publish' OR $wpdb->posts.post_status = 'private') 

          IF ( $drive )
          AND ( ($wpdb->postmeta.meta_key = 'vehicle_year' AND CAST($wpdb->postmeta.meta_value AS CHAR) = '$year')
          ELSEIF ( $fuel  )
          AND ( ($wpdb->postmeta.meta_key = 'vehicle_fuel' AND CAST($wpdb->postmeta.meta_value AS CHAR) = '$fuel')
          ENDIF

          AND ( ($wpdb->postmeta.meta_key = 'vehicle_fuel' AND CAST($wpdb->postmeta.meta_value AS CHAR) = '$fuel') )
          GROUP BY $wpdb->posts.ID 
          ORDER BY $wpdb->posts.post_date 
          DESC LIMIT 0, 99";

Answer 1

$p="";
$q="";
if( empty($drive) ){
    $p=" AND ( ($wpdb->postmeta.meta_key = 'vehicle_year' AND CAST($wpdb->postmeta.meta_value AS CHAR) = '$year')";
    }else{
        if( empty($fuel)  ){
            $q=" AND ( ($wpdb->postmeta.meta_key = 'vehicle_fuel' AND CAST($wpdb->postmeta.meta_value AS CHAR) = '$fuel')";
        }
    }

$query = "SELECT $wpdb->posts.ID
    FROM $wpdb->posts 
    INNER JOIN $wpdb->postmeta ON ($wpdb->posts.ID = $wpdb->postmeta.post_id)
    WHERE 1=1 
    AND $wpdb->posts.post_type = 'cars' 
    AND ($wpdb->posts.post_status = 'publish' OR $wpdb->posts.post_status = 'private') 
    ".$p.$q."
    AND ( ($wpdb->postmeta.meta_key = 'vehicle_fuel' AND CAST($wpdb->postmeta.meta_value AS CHAR) = '$fuel') )
    GROUP BY $wpdb->posts.ID 
    ORDER BY $wpdb->posts.post_date 
    DESC LIMIT 0, 99";