按行对表分组的列进行计数

Question

I can count number of a table rows by using mysqli_num_rows . I have a table which contains similar rows. How can I count by grouping by similar row? For instance: I have a table with 2 columns : Student and Option . Let say there are 50 students. 20 are in Economy option, 20 are in Management option and 10 are in Secretary Option. How can display those numbers. I can display only the 50.

my codes

$qry = "select * from table group by option";
$req= @mysqli_query($conn, $qry); 

$result = mysqli_query( $conn, "select id from table");
$num_rows = mysqli_num_rows($result); 

Students Total (<?php echo $num_rows ?>)

<table >
    <tr>
        <th>Student</th>
        <th>Option</th>
    </tr>
    <?php
    while($row=mysqli_fetch_array($req))

    {
    ?>
    <tr>
        <td><?php echo $row['student'] ?></td>
        <td><?php echo $row['option'] ?></td>
    </tr>
    <?php
    }
    ?>
</table>

Answer 1

Here is the query you need:

SELECT COUNT(*) AS `option_count`, * -- returns a count aliased as "options_count"
FROM `table`
GROUP BY `option` -- will group the options and show the counts

Now you can echo the count, along with other data:

echo $row['count_options'];
echo $['options'];

The problem that you have here is that you will not be able to display each student in the option because this counts / groups only the three options.

Answer 2

看到正确的查询：

$qry = "select option as opt, COUNT(*) AS option from table group by option";