如何在不重复php中显示值的情况下显示mysql数据库中的值

Question

When Iam showing database value from table its just repeating them according to content. First table which is content.

 id | category_id  |  name
-----------------------------
 1  |     2        |  Jason
 2  |     1        |  Richard
 3  |     2        |  John

category table:-

 id | name
 ---------
  1 | Manager
  2 | Employee

I use query:

$query=mysql_query("SELECT * FROM content");
while($row=mysql_fetch_array($query)){
                 $data[] = array('id'=> $row['id'],
                                'category_id' => $row['category_id'], 
                                'name' => $row['name']
                           );
            }
  for($i=0;$i<count($data);$i++){
     echo $data[$i]['category_id'];
     echo $data[$i]['name']."<br/>";
  }

  OUTPUT:-
  2 Jason 
  2 John
  1 Richard

But what i want is:-

 OUTPUT:-
 2 Jason John
 1 Richard

Now when echo out the result it shows me category_id 2 times having category_id=2 with its 2 name but what i want is to show only category_id 1 times and its corresponding 2 name of category_id=2. Please help.

Answer 1

Try this approach, it worked for me:

$query = mysql_query("SELECT COUNT(*), category_id, name, 

 GROUP_CONCAT(name separator ' ') as name FROM content  
 WHERE category_id=1 OR category_id=2 GROUP BY category_id 
 ORDER BY category_id DESC");

    while($row=mysql_fetch_array($query)){

        echo $row['category_id'] . " " . $row['name'] . "<br>";

    }

---

Plus, just a quick note about mysql_* functions being deprecated.

Use mysqli with prepared statements , or PDO with prepared statements , they're much safer.

Answer 2

Use this query:

SELECT id, category_id, GROUP_CONCAT(name SEPARATOR ' ') AS name
FROM content
GROUP BY category_id

See here for some quick tutorials on how to use GROUP BY and GROUP_CONCAT:
w3schools.com / GROUP BY
mysqltutorial.org / GROUP_CONCAT

Answer 3

You shouldn't be using mysql as it is deprecated so to help you along I've done this with PDO to show its not as daunting as you may think.

PDO connection to database:

try{
    $db = new PDO ('mysql:host=YourHost;dbname=YourDatabaseName', 'YourDatabaseUserName', 'YourDatabasePassword');
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}catch(PDOException $e){
    echo $e->getMessage();
    die();
}

The above connection uses aa try catch with a way of making any errors cleaner and easier to read by making use of the getMessage() function which removes a lot of the un needed info.

The query you're after in PDO:

$sql = "SELECT GROUP_CONCAT(name SEPARATOR ' ') AS names FROM yourtable GROUP BY category_id";
$query = $db->query($sql);
$results = $query->fetchAll(PDO::FETCH_OBJ);

foreach($results as $result){
    echo "<pre>", ($result->names), "</pre>";
}

This is the most basic way to use PDO to query your database but if you start using it like this you will find it easier to then develop the more in depth and secure ways of putting data in and getting data out of your database that help to prevent sql injection.

Hope this is a little food for thought and helps in getting you to move to a more secure API.

Answer 4

try this

select DISTINCT(*) from content or you can be more specific with ie DISTINCT(columnname)

Answer 5

<?php

// Using MySQL GROUP_CONCAT

$sql = 'SELECT category_id, GROUP_CONCAT(name separator \' \') FROM content GROUP BY category_id';


// Or PHP reduce as below
// Dummy Records
$records = [
    ['id' => 1, 'category_id' => 2, 'name' => 'Jason'],
    ['id' => 2, 'category_id' => 1, 'name' => 'Richard'],
    ['id' => 3, 'category_id' => 2, 'name' => 'John']
];

$result = array_reduce($records, function($carry, $record) {
    if (!array_key_exists($record['category_id'], $carry)) {
        $carry[$record['category_id']] = [];
    }

    $carry[$record['category_id']][] = $record['name'];

    return $carry;
}, []);

foreach ($result as $categoryId => $names) {
    echo $categoryId . ' ' . implode(' ', $names) . "\n";
}