如何提取和展平 MySQL 8 中 JSON 對象內部的數組？

Question

給定一些 json 文件，如下所示：

{
   "_id":"00006073",
    "subscribersIds":[
      170968,
      225647
   ]
}
-----------------------------------
{
   "_id":"00006072",
   "subscribersIds":[
      170968
   ]
}
--------------------------------
{
   "_id":"00006074,
   "subscribersIds":[
      228195,
      225647
   ]
}

你知道我怎樣才能得到一個subscribersIds的列表，而不用重復嗎？ 結果應該是這樣的170968, 225647, 228195 ，因為我需要將此查詢的結果用作另一個查詢的條件。

對於 Couchebase，有“UNNEST”命令可以執行此操作，但是我在 MySQL 8 中找不到正確的方法，因為SELECT DISTINCT doc ->> '$.subscribersIds[*]' FROM customers will return [170968,225647],[170968],[228195,225647]

提前致謝！

Answer 1

mysql> select * from mytable;
+----------+------------------+
| _id      | subscriberIds    |
+----------+------------------+
| 00006072 | [170968]         |
| 00006073 | [170968, 225647] |
| 00006074 | [228195, 225647] |
+----------+------------------+

mysql> select j.subscriberId from mytable, 
  json_table(mytable.subscriberIds, '$[*]' columns (subscriberId int path '$')) j;
+--------------+
| subscriberId |
+--------------+
|       170968 |
|       170968 |
|       225647 |
|       228195 |
|       225647 |
+--------------+

mysql> select distinct j.subscriberId from mytable,
  json_table(mytable.subscriberIds, '$[*]' columns (subscriberId int path '$')) j;
+--------------+
| subscriberId |
+--------------+
|       170968 |
|       225647 |
|       228195 |
+--------------+

這是一個相當復雜的查詢，每次您想要獲取一組不同的subscriberId 時都要編寫。

如果您根本不使用 JSON 而是以標准化方式存儲 id，每行一個在第二個表中，這會容易得多。

mysql> create table mySubscribers (_id char(8), subscriberId int, primary key (_id, subscriberId));

mysql> insert into mySubscribers (_id, subscriberId) select _id, subscriberId from mytable, json_table(subscriberIds, '$[*]' columns (subscriberId int path '$')) j;
Records: 5  Duplicates: 0  Warnings: 0

mysql> select * from mySubscribers;
+----------+--------------+
| _id      | subscriberId |
+----------+--------------+
| 00006072 |       170968 |
| 00006073 |       170968 |
| 00006073 |       225647 |
| 00006074 |       225647 |
| 00006074 |       228195 |
+----------+--------------+

mysql> select distinct subscriberId from mySubscribers;
+--------------+
| subscriberId |
+--------------+
|       170968 |
|       225647 |
|       228195 |
+--------------+