SQL Select 语句加入 [重复]

Question

我有一个 oc_category_description 表，其中列是：

• category_id
• 姓名

以及列所在的其他表 oc_category：

• category_id
• 图片
• parent_id

这里是 oc_category_description 表的示例图片

oc_category 表

这里我想显示名字、category_id、image、parent_id，其中oc_category parent_id 为0；

这里是sql：

php

function getMainCategory()
{
    $stmt = $this->con->prepare("SELECT category_id, image, parent_id, (SELECT oc_category_description.name FROM oc_category_description WHERE oc_category.category_id = oc_category_description.category_id) FROM oc_category WHERE parent_id = 0 ORDER BY category_id ASC");

    $stmt->execute();
    $stmt->bind_result($category_id, $image, $parent_id, $name);

    $users = array();

    while ($stmt->fetch()) {
        $temp = array();
        $temp['category_id'] = $category_id;
        $temp['image'] = $image;
        $temp['parent_id'] = $parent_id;
        $temp['name'] = $name;

        array_push($users, $temp);
    }
    return $users;
}

但它什么也没返回:(

Answer 1

使用连接

SELECT ocd.category_id, image, parent_id, name
FROM oc_category_description  AS ocd
INNER JOIN oc_category 
WHERE parent_id = 0 
ORDER BY ocd.category_id ASC

Answer 2

使用 INNER JOIN：

SELECT d.category_id, c.image, c.parent_id, d.name
FROM oc_category_description  d INNER JOIN oc_category c
ON c.category_id = d.category_id
WHERE c.parent_id = 0 
ORDER BY d.category_id

如果结果中出现重复行，则更改为：

SELECT DISTINCT...