PHP MYSQL聯合查詢

Question

我是mysql查詢的新手，無法獲取所需的數據結構。 我希望你們中的一員能提供幫助。

我有以下查詢：

SELECT *
FROM wp_postmeta
WHERE post_id IN (SELECT id from wp_posts WHERE post_type = 'product')

它只是從表2中獲取與表1中的產品具有相同ID的所有數據。問題是結果返回為：

{meta_id: "37230", post_id: "2549", meta_key: "total_sales", meta_value: "0"}
{meta_id: "37231", post_id: "2549", meta_key: "_virtual", meta_value: "no"}
{meta_id: "37232", post_id: "2549", meta_key: "_tax_status", meta_value: "taxable"}
{meta_id: "37233", post_id: "2549", meta_key: "_visibility", meta_value: "visible"}
{meta_id: "37234", post_id: "2549", meta_key: "_featured", meta_value: "no"}
{meta_id: "37235", post_id: "2549", meta_key: "_weight", meta_value: "0.50"}
{meta_id: "37236", post_id: "2549", meta_key: "_sku", meta_value: "HCS-DGMP"}
{meta_id: "37237", post_id: "2549", meta_key: "_product_attributes", meta_value: "a:0:{}"}
{meta_id: "37238", post_id: "2549", meta_key: "_regular_price", meta_value: "18.99"}
{meta_id: "37239", post_id: "2549", meta_key: "_sale_price", meta_value: ""}

如您所見，它們都具有相同的帖子ID，但是在單獨的對象中返回。 如何修改上面的查詢，以便所有查詢都返回一個對象？ 我還將刪除meta_id因為它沒有用。

Answer 1

從MySQL 5.7.22開始，您可以使用JSON_OBJECTAGG(key, value) ：

SELECT post_id, JSON_OBJECTAGG(meta_key, meta_value) AS meta_data
FROM wp_postmeta
WHERE post_id IN (SELECT id from wp_posts WHERE post_type = 'product')
GROUP by post_id

這將以key: value對的形式將meta_data作為JSON_OBJECT返回：

post_id | meta_data
   2549 | {"_sku": "HCS-DGMP", "_weight": "0.50", "_virtual": "no", "_featured": "no", "_sale_price": null, "_tax_status": "taxable", "_visibility": "visible", "total_sales": "0", "_regular_price": "18.99", "_product_attributes": "a:0:{}"}

演示版

如果您的服務器不支持JSON_OBJECTAGG() ，我將使用PHP解決方案：

$postIds = array_unique(array_column($dbResult, 'post_id'));

$posts = [];
foreach ($postIds as $id) {
    $posts[$id] = (object)['id' => $id];
}

foreach ($dbResult as $row) {
    $posts[$row->post_id]->{$row->meta_key} = $row->meta_value;
}

echo json_encode(array_values($posts), JSON_PRETTY_PRINT);

結果：

[
    {
        "id": "2549",
        "total_sales": "0",
        "_virtual": "no",
        "_tax_status": "taxable",
        "_visibility": "visible",
        "_featured": "no",
        "_weight": "0.50",
        "_sku": "HCS-DGMP",
        "_product_attributes": "a:0:{}",
        "_regular_price": "18.99",
        "_sale_price": ""
    }
]

演示版

只要您不處理數千行，我就不必擔心性能。