分组和计数PDO输出

Question

我有一个查询：

$myData = $db->query("
         SELECT * 
         FROM t1
         WHERE event = '$eid'
         ", PDO::FETCH_OBJ);

以数组形式返回结果：

Array (
[0] => stdClass Object
    (
        [id] => 1
        [even] => 1
        [response] => NO
        [adult] => 
        [child] => 
    )

[1] => stdClass Object
    (
        [id] => 2
        [event] => 1
        [response] => YES
        [adult] => 1
        [child] => 3
    )
)

我需要得到以下计数：

每个响应的总计：是和否如是：成人总数儿童总数

我可以从查询中获取它，还是需要操纵该数组以获取计数？

Answer 1

您可以使用条件计数和求和。为此，CASE语句非常好。

SELECT 
    COUNT(CASE response WHEN 'YES' THEN 1 ELSE NULL END) as YesResponses, 
    COUNT(CASE response WHEN 'NO' THEN 1 ELSE NULL END) as NoResponses, 
    SUM(CASE response WHEN 'YES' THEN adult ELSE 0 END) as Adults, 
    SUM(CASE response WHEN 'YES' THEN child ELSE 0 END) as Children 
FROM t1

但是，请注意，您的代码容易受到SQL注入的攻击。您需要使用参数化的prepared statement。

Answer 2

您可以从当前查询中迭代结果数组，也可以从另一个查询中获取计数。

-- display count of YES responses and total adults and children
SELECT COUNT(*), SUM(adult), SUM(child) 
    FROM t1
    WHERE event = '$eid'
    AND response = 'YES';

-- display count of NO responses
SELECT COUNT(*)
    FROM t1
    WHERE event = '$eid'
    AND response = 'NO';

可能最好在准备好的语句中使用它们。

https://www.php.net/manual/en/pdo.prepare.php

https://www.php.net/manual/en/pdo.prepared-statements.php