在BigQuery中，可以使用STRUCT和ARRAY来创建具有动态键的地图。下面是一个示例代码，演示如何在BigQuery中创建和查询具有动态键的地图：

1. 创建一个包含地图的表：

CREATE TABLE my_table (
  id INT64,
  my_map ARRAY>
);

2. 插入数据到表中：

INSERT INTO my_table (id, my_map)
VALUES (1, [
  STRUCT('key1' AS key, 10 AS value),
  STRUCT('key2' AS key, 20 AS value),
  STRUCT('key3' AS key, 30 AS value)
]),
(2, [
  STRUCT('key4' AS key, 40 AS value),
  STRUCT('key5' AS key, 50 AS value)
]);

3. 查询表中的地图数据：

SELECT id, my_map
FROM my_table;

这将返回以下结果：

id  |  my_map
----+--------------------------------------------------
1   |  [{"key": "key1", "value": 10}, {"key": "key2", "value": 20}, {"key": "key3", "value": 30}]
2   |  [{"key": "key4", "value": 40}, {"key": "key5", "value": 50}]

4. 查询特定键的值：

SELECT id, ARRAY(SELECT AS STRUCT key, value FROM UNNEST(my_map) WHERE key = 'key1') AS my_map_key1
FROM my_table;

这将返回以下结果：

id  |  my_map_key1
----+---------------
1   |  [{"key": "key1", "value": 10}]
2   |  NULL

以上是在BigQuery中使用STRUCT和ARRAY来创建和查询具有动态键的地图的示例代码。您可以根据自己的需求进行修改和扩展。