如何对不同条件下同一张表中的数据求和？答案

【问题标题】：How to sum data from the same table with different condition?如何对不同条件下同一张表中的数据求和？
【发布时间】：2017-08-17 15:54:09
【问题描述】：

我从同一个表名中获取了一些数据，但条件不同，我查询了 3 次，结果是：

101=>1
301=>1
501=>2
502=>4
---------------
101=>2
501=>1
---------------
101=>1
501=>1

第一列是教室，第二列是价值观。将这些值与同一教室相加的最佳方法是什么，结果将是：

我的查询命令：

$query = $db->prepare("SELECT COUNT(std_id) AS total, std_class  FROM attendance WHERE att_mode IN('mode-01','mode-04') AND att_attend='0' AND att_date=CURDATE()  GROUP BY std_class ORDER BY std_class");
    $query->execute();
    while ($char = $query->fetch(PDO::FETCH_OBJ)) {
        $labels2[] = $char->std_class.'-'.$char->total;
        $link[] = $char->std_class;
    }
$query = $db->prepare("SELECT COUNT(std_id) AS total_sick,std_class FROM attendance WHERE att_mode ='mode-01' AND att_attend='2' AND att_date=CURDATE()  GROUP BY std_class ORDER BY std_class");
    $query->execute();
    while($char = $query->fetch(PDO::FETCH_OBJ)){
        $sickCount[] = $char->std_class.'-'.$char->total_sick;
    }
$query = $db->prepare("SELECT COUNT(std_id) AS total_leave,std_class FROM attendance WHERE att_mode ='mode-01' AND att_attend='3' AND att_date=CURDATE()  GROUP BY std_class ORDER BY std_class");
    $query->execute();
    while($char = $query->fetch(PDO::FETCH_OBJ)){
        $leaveCount[] = $char->std_class.'-'.$char->total_leave;
    }

【问题讨论】：

标签： php sum

【解决方案1】：

使用子查询试试这个。

"SELECT std_class , COUNT(std_id) as total ,(SELECT COUNT(std_id) AS total_sick FROM attendance WHERE att_mode ='mode-01' AND att_attend='2' AND att_date=CURDATE()  GROUP BY std_class ORDER BY std_class ) AS total_sick    , (SELECT COUNT(std_id) FROM attendance WHERE att_mode ='mode-01' AND att_attend='3' AND att_date=CURDATE()  GROUP BY std_class ORDER BY std_class) AS total_leave FROM attendance WHERE att_mode IN('mode-01','mode-04') AND att_attend='0' AND att_date=CURDATE()  GROUP BY std_class ORDER BY std_class "

如果不工作，请告诉我...

【讨论】：

我收到了这个错误：SQLSTATE[21000]: Cardinality violation: 1242 Subquery return more than 1 row

【解决方案2】：

编辑：Priyank 的答案显然更好，因为它是通过 SQL 完成的，所以没有 PHP 开销。

我会获取每个查询的结果，将其粘贴到关联数组中，然后循环它们。它看起来像这样：

$result = db_query1();
$total = array();
foreach ($result as $classroom => $value) {
    $total[$classroom] += $value;
}

$result = db_query2();
foreach ($result as $classroom => $value) {
    $total[$classroom] += $value;
}

$result = db_query3();
foreach ($result as $classroom => $value) {
    $total[$classroom] += $value;
}

print_r($total);

【讨论】：

【解决方案3】：

如前所述，Priyank 的答案应该是要走的路，但是因为在看到其他答案之前，我为你写了一个小函数，所以无论如何我都会发布它，因为如果你不想要它可能会很有用任何理由都可以在 SQL 中完成。

function mergeAndSum() {
    // get all the given arguments and put them into an array
    $arrays = func_get_args();

    // create an array that will contain the output
    $output = array();

    // loop through all the arguments
    foreach($arrays as $array) {
        // if an argument is not an array it will be skipped
        if(!is_array($array)) {
            continue;
        }
        // otherwise it will be iterated
        foreach($array as $key => $value) {
            // if the key is already in the $output array
            if(array_key_exists($key,$output)) {
                // add the value to the existing onve for that key
                $output[$key] += $value;
            } else {
                // else store in the $output array the key with it's value
                $output[$key] = $value;
            }

        }

    }

    return $output;

}

所以，假设您有三个包含查询结果的数组

$link = array(
    101=>1,
    301=>1,
    501=>2,
    502=>4,
);
$sickCount = array(
    101=>2,
    501=>1
);
$leaveCount = array(
    101=>1,
    501=>1
);

你只需将它们传入

$output = mergeAndSum($link,$sickCount,$leaveCount);

你的 $output 会如你所愿

请记住，SQL 方式会更好，此函数足够灵活，可用于其他类似情况，即您需要合并和求和一些数组

【讨论】：

【解决方案4】：

我终于找到了解决办法。我没有进行 3 次查询，而是只运行一个查询。工作查询是：

$query = $db->prepare("SELECT COUNT(std_id) AS total, std_class FROM attendance WHERE att_mode IN('mode-01','mode-04') AND att_attend IN('0','2','3') AND att_date=CURDATE() GROUP BY std_class ORDER BY std_class");

“WHERE”子句将满足包含“0”、“2”和“3”值的“att_mode”。然后我得到了想要的结果。感谢您之前的所有回答。

【讨论】：