即使ID匹配，SQL INNER JOIN也仅从第二个表中选择最后一行

Question

How to select all rows by id from second table? At the moment it selects only last row from second table if id matches.

Query:

SELECT

categories.category_id,
categories.category_name,
subcategories.subcategory_name,
categories.category_data,
categories.category_icon

FROM categories INNER JOIN subcategories ON

subcategories.category_id=categories.category_id";

Full code:

public static function getAllCategories()
{
    $database = DatabaseFactory::getFactory()->getConnection();

    $sql = "
    SELECT c.category_id
         , c.category_name
         , s.subcategory_name
         , c.category_data
         , c.category_icon 
      FROM categories c
      JOIN subcategories s 
        ON s.category_id = c.category_id;
     ";

    $query = $database->prepare($sql);
    $query->execute();

    $all_categories = array();

    foreach ($query->fetchAll() as $category) {

        array_walk_recursive($category, 'Filter::XSSFilter');

        $all_categories[$category->category_id] = new stdClass();
        $all_categories[$category->category_id]->category_id = $category->category_id;
        $all_categories[$category->category_id]->category_data = $category->category_data;
        $all_categories[$category->category_id]->category_icon = $category->category_icon;
        $all_categories[$category->category_id]->category_name = $category->category_name;
        $all_categories[$category->category_id]->subcategory_name = $category->subcategory_name;
    }

    return $all_categories;
}

Photos:

This is what I should get:

And this is what I have:

First table properly selects all rows, but second table selects only last row if id matches. How to select all rows from second table?

Answer 1

The problem is in your PHP. Each time through the loop you replace $allCategories[$category->category_id] with the data from the current row. So when the loop is done, it only contains the data from the last row.

You should make a multidimensional array. When a row contains the same category as a previous row, push the new object onto the array.

foreach ($query->fetchAll() as $category) {

    array_walk_recursive($category, 'Filter::XSSFilter');

    if (!isset($allCategories[$category->category_id])) {
        $allCategories[$category->category_id] = array();
    }
    $all_categories[$category->category_id][] = $category;
}

There's no need to make a new stdClass object and copy each property, since fetchAll returns a new object for each row. You can just put that object into the array.

Answer 2

Query:

SELECT

categories.category_id,
categories.category_name,
subcategories.subcategory_id,
subcategories.subcategory_name,
categories.category_data,
categories.category_icon

FROM categories INNER JOIN subcategories ON

subcategories.category_id=categories.category_id";

EDIT

$subCat = array();
foreach ($query->fetchAll() as $category) {

     array_walk_recursive($category, 'Filter::XSSFilter');

     $subCat[$category->category_id][] = $category->subcategory_name;

     $all_categories[$category->category_id] = new stdClass();
     $all_categories[$category->category_id] = $category;
     $all_categories[$category->category_id]->subcategory_name = (object) $subCat[$category->category_id];
}

While getting the data:

<?php foreach ($this->categories as $category) { ?>
    <?= $category->category_data; ?>
    <?php foreach ($category->subcategory_name as $subcategory) { ?>
        <?= $subcategory; ?>
    <?php } ?>
<?php } ?>