PHP PDO-使用MySQL变量 [英] PHP PDO - Using MySQL Variables

问题描述

我正在尝试使用PDO在PHP中运行查询. 该查询在顶部具有一些变量来确定排名，除了在$ sql中使用SET @var时，它返回一个空行集.但是，如果删除有问题的SQL，它将返回正常状态.

I'm trying to run a query in PHP using PDO. The query has some variables at the top to determine a rank, except the when using the SET @var in the $sql, it returns an empty rowset. If I remove the offending SQL however, it returns fine.

我不想在脚本中返回@ prev_value，@ rank_count或@rank_increasing，而只返回它在SELECT中创建的排名.

I don't want to return @prev_value, @rank_count or @rank_increasing in my script, only the rank it creates in the SELECT.

能否让我知道我在做什么错?

Can you let me know what I am doing wrong please?

谢谢

    $sql = "
    SET @prev_value = NULL;
    SET @rank_count = 0;
    SET @rank_increasing = 0;
    SELECT a.*
         , @rank_increasing := @rank_increasing + 1 AS row_num
         , CASE
           WHEN @prev_value = score 
              THEN @rank_count
           WHEN @prev_value := score 
              THEN @rank_count := @rank_increasing
           END AS rank
      FROM ( 
           -- INLINE VIEW --
           ) a
    ";
    try {
        $sth = $dbh->prepare($sql);
        $sth->execute(array($var1, $var2));
        return $sth->fetchAll(PDO::FETCH_ASSOC);
    } catch (Exception $e) {
        return $e;
    }

推荐答案

在此处找到解决方案: https://stackoverflow.com/a/4685040/1266457

Found the solution here: https://stackoverflow.com/a/4685040/1266457

谢谢:)

要解决:

// Prepare and execute the variables first
$sql = "
SET @prev_value = NULL;
SET @rank_count = 0;
SET @rank_increasing = 0;
";
$sth = $dbh->prepare($sql);
$sth->execute();

// Run the main query
$sql = "
SELECT a.*
     , @rank_increasing := @rank_increasing + 1 AS row_num
     , CASE
       WHEN @prev_value = score 
          THEN @rank_count
       WHEN @prev_value := score 
          THEN @rank_count := @rank_increasing
       END AS rank
  FROM ( 
       -- INLINE VIEW --
       ) a
"; ...

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