Question

我有一个promblem来计算来自一列不同的行，这是我的数据库和查询

$host = 'localhost';
$db   = 'cbt';
$user = 'root';
$pass = '';

$dsn = "mysql:host=$host;dbname=$db";
$pdo = new PDO($dsn, $user, $pass);

$matematika = 'MTK';
$soal_mtk = $pdo->prepare("select count(*) from cbt.data_ujian where data_ujian.id_mapel = :mtk");
$soal_mtk->bindParam(':mtk', $matematika, PDO::PARAM_STR, 12);
$soal_mtk->execute();
$mtk = $soal_mtk->fetchColumn();

$fisika = 'FIS';
$soal_fis = $pdo->prepare("select count(*) from cbt.data_ujian where data_ujian.id_mapel = :fis");
$soal_fis->bindParam(':fis', $fisika, PDO::PARAM_STR, 12);
$soal_fis->execute();
$fis = $soal_fis->fetchColumn();

$kimia = 'KIM';
$soal_kim = $pdo->prepare("select count(*) from cbt.data_ujian where data_ujian.id_mapel = :kim");
$soal_kim->bindParam(':kim', $kimia, PDO::PARAM_STR, 12);
$soal_kim->execute();
$kim = $soal_kim->fetchColumn();

我能用一个查询计算所有这些吗？请告诉我是否需要更多信息。非常感谢你。

Answer 1

是的，你可以，你需要在WHERE条件下使用GROUP BY。像这样，

SELECT count(*),
       data_ujian.id_mapel
FROM cbt.data_ujian
WHERE (data_ujian.id_mapel = :mtk
       OR data_ujian.id_mapel = :fis
       OR data_ujian.id_mapel = :kim)
GROUP BY data_ujian.id_mapel

以上查询会按id_mapel列对结果进行分组，并从每个类别中提供count。

Answer 2

如果我理解你，GROUP BY子句应该按照你的要求行事：

SELECT count(*), id_mapel FROM cbt.data_ujian GROUP BY id_mapel

Answer 3

尝试以下查询 -

SELECT Sum(data_ujian.id_mapel = 'mtk') AS 'mtk', 
       Sum(data_ujian.id_mapel = 'fis') AS 'fis', 
       Sum(data_ujian.id_mapel = 'kim') AS 'kim', 
FROM   cbt.data_ujian;

如何计算具有不同值的一列中的行

3 个答案: