SQL选择重复日期的计数

Question

我正在尝试选择重复日期的计数并输出其数字

$user_curr_id = $_SESSION['user_id'];
$sql = "SELECT COUNT(datum) FROM table_name WHERE user_ids = $user_curr_id";

我不知道该怎么做。

2014-07-23,2014-07-23,2014-07-23 => 3
2014-07-24,2014-07-24 =>2
2014-07-25 => 1

并获取$result = 3,2,1

Answer 1

我假设你正在照看GROUP BY子句：

$sql = "SELECT datum, COUNT(datum) as cnt
        FROM table_name 
        WHERE user_ids = $user_curr_id 
        GROUP BY datum
        ORDER BY COUNT(datum) DESC;";

如果您的列datum属于数据类型DATE。

注意

如前所述，您很容易受到sql注入攻击。您应该使用参数化的预准备语句并将输入值绑定到此参数，如：

$sql = "SELECT datum, COUNT(datum) cnt
        FROM table_name 
        WHERE user_ids = ? 
        GROUP BY datum
        ORDER BY COUNT(datum) DESC;";

$result = array();
if ($stmt = $mysqli->prepare($sql)) {
    if ($stmt->bind_param('s', $user_curr_id)) {
        if($res = $stmt->execute()) {
            while ($row = $res->fetch_assoc()) {
                $result[] = $row['cnt'];             // add the content of field cnt
            }
        }
    }
}
echo implode(',', $result);