SQL Select 语句加入

Question

我有一个 table of oc_category_description 其中列是：

category_id
姓名

和其他 table oc_category 其中列为：

category_id
图片
parent_id

这里是oc_category_descriptiontable

的示例图片

oc_category table

这里我想显示名字，category_id，图片，parent_id 其中 oc_category parent_id 是 0；

这是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;
}

但是returns没什么:(

Answer 1

使用加入

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，请更改为：

SELECT DISTINCT...

SQL Select 语句加入

SQL Select Statement joining

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