问题描述

我正在更新表中的一行，并尝试按照 这个答案.

I am updating a row in a table, and trying to return the updated row, as per this SO answer.

我的代码如下:

$sql = "SET @update_id := '';
        UPDATE testing SET status='1', id=(SELECT @update_id:=id)
        WHERE status='0' LIMIT 1; 
        SELECT @update_id;";

$db->beginTransaction();
try{
    $stmt = $db->prepare($sql);
    $stmt->execute();

    echo count($stmt->fetchAll());

    $db->commit();
}catch(Exception $e){
    echo $e->getMessage();
    exit();
}

但我总是收到以下错误

SQLSTATE[HY000]:一般错误

SQLSTATE[HY000]: General error

根据 $stmt->fetchAll()-general-error-when-updating-database?#answer-12980031">这个答案.如果我去掉那行，该行会适当更新.

Which seems to be due to the $stmt->fetchAll(), according to this SO answer. If I take that line out, the row is updated appropriately.

那么，如何使用 PDO 运行多查询语句(多语句查询！?)，并从 SELECT 中获取结果?

So, how do I run the multi-query statement (multi-statement query!?) using PDO, and obtain the results from the SELECT?

编辑 1

我不需要需要更新行的计数.我需要该行的实际 ID.

I DO NOT need the count of the rows updated. I need the actual ID of the row.

表架构

  id   |   someCol  |  status
 ----- |   -------  |  ------
   1   |     123    |    0
   2   |     456    |    0
   3   |     789    |    0
   4   |     012    |    0

• 看看桌子，
• 找到第一个状态=0，
• 更新行，
• 返回更新行的id

我对计数的兴趣为零，因为查询已将 LIMIT 1 硬编码到其中.

The count is of zero interest to me, as the query has LIMIT 1 hard-coded into it.

直线的整个点

count($stmt->fetchAll());

是通过/失败条件.

if(count ==1){
    ... do something with the returned id ...
}else{
    ... do something else ...
}

编辑 2

显然，这个问题很容易通过两个单独的查询来解决.我更愿意在一个查询中使用它.既是一种偏好，也是学习的机会.

Obviously this issue is simple to get around with two separate queries. I would prefer to have this in one single query. Both a preference, as well as an opportunity to learn.

推荐答案

您需要将 SELECT @update_id 作为单独的查询进行 -- 您不能将多个查询放在一个语句中.这样做:

You need to do the SELECT @update_id as a separate query -- you can't put multiple queries in a single statement. So do:

$sql = "SET @update_id := '';
        UPDATE testing SET status='1', id=(SELECT @update_id:=id)
        WHERE status='0' LIMIT 1";
try{
    $db->beginTransaction();
    $db->query($sql); // no need for prepare/execute since there are no parameters
    $stmt = $db->query("SELECT @update_id");
    $row = $stmt->fetch(PDO::FETCH_ASSOC);
    $id = $row['@update_id'];
    $db->commit();
} catch (Exception $e) {
    echo $e->getMessage();
    $db->rollBack();
    exit();
}

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