php - 如何使用 PHP MYSQL 计算特定类别的记录数

Question

我正在尝试显示特定类别的记录数。

就像stackoverflow在相关标签部分显示的一样。

http://stackoverflow.com/questions

javascript × 943089
java × 926620
c# × 848261
php × 807008 

我正在使用这个代码。

<?php 
    $query = mysqli_query($conn, "SELECT COUNT(*) as num FROM data where category = 'android'");
    while ($row = mysqli_fetch_array($query)) {
    echo 'Android = '.$row['num'].'<br>';
    }

    $query = mysqli_query($conn, "SELECT COUNT(*) as tot FROM data where category = 'ajax'");
    while ($row = mysqli_fetch_array($query)) {
    echo 'Ajax = '.$row['tot'].'<br>';
    }   

    $query = mysqli_query($conn, "SELECT COUNT(*) as det FROM data where category = 'php'");
    while ($row = mysqli_fetch_array($query)) {
    echo 'PHP = '.$row['det'].'<br>';
    }

?>

它工作正常，但我不想使用那么多 SQL 查询。

如何使用单个 SQL 查询实现这一点？

Answer 1

尝试使用 group by 子句

$query = mysqli_query($conn, "SELECT category, COUNT(*) as num FROM data where category in ( `PHP`, `MYSQL`, `JAVA`, `AJAX`  ) group by category");
while ($row = mysqli_fetch_array($query)) {
   echo $row['category'] . ' = '.$row['num'].'<br>';
 }