Question

我在列extra_fields中有一个带有JSON数组的数据库。我需要通过id提取一个值。

JSON看起来像这样，尽管每行的对象数量是随机的：

[
{"id":"1","value":"48768"},
{"id":"2","value" ["String","http:someurl"]},
{"id":"5","value":"somevalue"},
{"id":"6","value":""},
{"id":"8","value":"Op-Ed"},
{"id":"9","value":"8111,13498,15408"},
{"id":"10","value":"30"},
{"id":"11","value":"This is the target string"}
]

我可以使用以下方法提取一组id：

SELECT extra_fields->>"$[*].id"  FROM esqt7_k2_items;

我可以使用以下方法提取值数组：

SELECT extra_fields->>"$[*].value"  FROM esqt7_k2_items;

我可以在第n个零序对象位置提取单个值：

SELECT extra_fields->>"$[2].value"  FROM esqt7_k2_items;

但问题是存在可变数量的对象，我特别需要object id = 11的值.JSON_EXTRACT似乎不支持过滤，因为JSONPATH的每个变体似乎都失败了。 $..[?(@.id=11)].value作为JSONPATH工作，但是这个（以及许多变体）都失败了：

SELECT extra_fields->"$.[?(@.id=11)].value" FROM esqt7_k2_items; #FAILS

这是一个迁移项目，JSON的东西就是Joomla选择实现额外字段的方式。如果你问我，有点痛。

Answer 1

您可以考虑一个选项（小心性能问题）：

mysql> SELECT VERSION();
+-----------+
| VERSION() |
+-----------+
| 5.7.19    |
+-----------+
1 row in set (0.00 sec)

mysql> DROP TABLE IF EXISTS `esqt7_k2_items`;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE IF NOT EXISTS `esqt7_k2_items` (
    ->   `id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
    ->   `extra_fields` JSON NOT NULL
    -> );
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO `esqt7_k2_items`
    ->   (`extra_fields`)
    -> VALUES
    ->   ('
    '>     [
    '>       {"id": "1", "value": "48768"},
    '>       {"id": "2", "value": ["String","http:someurl"]},
    '>       {"id": "5", "value": "somevalue"},
    '>       {"id": "6", "value": ""},
    '>       {"id": "8", "value": "Op-Ed"},
    '>       {"id": "9", "value": "8111,13498,15408"},
    '>       {"id": "10", "value": "30"},
    '>       {"id": "11", "value": "This is the target string"}
    '>     ]
    '>   '),
    ->   ('
    '>     [
    '>       {"id": "1", "value": ""},
    '>       {"id": "9", "value": "ONE This is the target string"}
    '>     ]
    '>   '),
    ->   ('
    '>     [
    '>       {"id": "6", "value": ""},
    '>       {"id": "11", "value": "TWO This is the target string"}
    '>     ]
    '>   ');
Query OK, 3 rows affected (0.00 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> SET @`search_id` := '11';
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT `der`.`id`, `der`.`value`
    -> FROM (
    ->   SELECT
    ->     `id`,
    ->     JSON_UNQUOTE(
    ->       JSON_EXTRACT(`extra_fields`,
    ->         CONCAT((SELECT
    ->           JSON_UNQUOTE(
    ->             JSON_SEARCH(`extra_fields` ->> '$[*].id', 'one', @`search_id`)
    ->           )
    ->                 FROM `esqt7_k2_items` `esqt7_k2_items_in`
    ->                 WHERE `esqt7_k2_items_out`.`id` = `esqt7_k2_items_in`.`id`
    ->                ), ".value"
    ->         )
    ->       )
    ->     ) `value`
    ->   FROM `esqt7_k2_items` `esqt7_k2_items_out`
    -> ) `der`
    -> WHERE `der`.`value` IS NOT NULL;
+----+-------------------------------+
| id | value                         |
+----+-------------------------------+
|  1 | This is the target string     |
|  3 | TWO This is the target string |
+----+-------------------------------+
2 rows in set (0.00 sec)

请参阅db-fiddle。

Answer 2

我发现最简单的方式

对象id = 11
的值

通过找到正确的＆＃34;索引＆＃34;所需对象，做一点 PHP 。首先，我们通过简单的请求获取所有对象ID：

public intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
  // Clone the request to add the new header.
  const clonedRequest = req.clone();

  clonedRequest.headers.set("ModuleId", this.dnnContext.moduleId);
  clonedRequest.headers.set("TabId", this.dnnContext.tabId);

  // Pass on the cloned request instead of the original request.
  return next.handle(clonedRequest);
}

然后在PHP中

> SELECT extra_fields->>"$[*].id"  FROM esqt7_k2_items;

然后通过传递 $ rightIndex ：

来获得正确的对象

$rightIndex = array_search($ids, '11');

简单如同地狱！您可以在其他任何地方执行相同的操作，例如，当您需要更新数组中的对象或其值/值等时。那就是干杯！

MySQL JSON通过id提取单个值

2 个答案: