counting occurrences of certain inputs in data table/database - php

Question

I am currently populating a data table on my website from information stored in a mysql database
The table is of the form:
Table 1
ID | DataA | Other Info | Count Data
======================================
1 | A | Other Info | 2
2 | B | Other Info | 3
Table 2
ID | Input
==========
1 | A
2 | A
3 | B
4 | B
5 | B
Count data in table 1 is intended to show how often the entry form the DataA column appears in the input column in Table2
Update....
CREATE TABLE driver (
`ID` INTEGER,
`DataA` VARCHAR(1),
`Other Info` VARCHAR(10),
primary key (ID)
);
$sql = "SELECT * FROM `driver` ORDER BY drivercompany";
$query = mysqli_query($conn, $sql);
if (mysqli_num_rows($query) > 0) {
// output data of each row
while ($result = mysqli_fetch_assoc($query)) {
echo "<tr>
<td class='class'>" . $result['id'] . "</td>
<td>" . $result['DataA'] . "</td>
<td>" . $result['otherinfo'] . "</td>
<td></td> /**count goes here**/
</tr>";
}
}
?>
using db fiddle, the query I need to get the count is:
SELECT driver.*, COUNT(add_job.Input) AS counter
FROM driver
LEFT JOIN add_job ON add_job.Input = driver.DataA
GROUP BY driver.ID
I have tried adding it to my code as so:
$sql = "SELECT * FROM `driver` ORDER BY drivercompany";
$query = mysqli_query($conn, $sql);
$count = "SELECT `driver`.*, COUNT(`add_job`.`adddriver`) AS counter
FROM `driver`
LEFT JOIN `add_job` ON `add_job`.`adddriver` = `driver`.`drivercompany`
GROUP BY `driver`.`id`";
$counter = mysqli_query($conn, $count);
while($result = mysqli_fetch_assoc($query,$counter)) { //and other variations
I cannot determine how to get $count and $query to work together

Answer 1

You can JOIN the two tables, group by the primary key of table1 and count the number of occurances in table2 with a single query.
Assuming ID is the primary key in table1, change your query to:
$sql = "
SELECT t1.*, COUNT(t2.Input) AS counter
FROM table1 t1
LEFT JOIN table2 t2 ON t2.Input = t1.DataA
GROUP BY t1.ID
";
The result would be:
| ID | DataA | Other Info | Count Data | counter |
| --- | ----- | ---------- | ---------- | ------- |
| 1 | A | Other Info | 2 | 2 |
| 2 | B | Other Info | 3 | 3 |
See the result in db-fiddle
Then you can use $result['counter'] in your output. Eg.:
echo "
<tr>
<td class='class'>{$result['id']}</td>
<td>{$result['DataA']}</td>
<td>{$result['otherinfo']}</td>
<td>{$result['counter']}</td>
</tr>
";
Note: If you have the ONLY_FULL_GROUP_BY mode enabled in MySQL < 5.7 or any version of MariaDB, the query will raise an error. In this case you should change it to
SELECT t1.id, t1.DataA, t1.otherinfo, COUNT(t2.Input) AS counter
FROM table1 t1
LEFT JOIN table2 t2 ON t2.Input = t1.DataA
GROUP BY t1.id, t1.DataA, t1.otherinfo
To include all selected non-aggreagted columns in the GROUP BY clause.