如何在sql中循环json数组以选择特定索引的值

示例数据

{ "type": "MultiPolygon", 
    "coordinates": [
        [
            [[40, 40], [20, 45], [45, 30], [40, 40]]
        ], 
        [
            [[20, 35], [10, 30], [10, 10], [30, 5], [45, 20], [20, 35]], 
            [[30, 20], [20, 15], [20, 25], [30, 20]]
        ]
    ]
}

Sql 代码

SELECT polygons.[key] as polygon, lines.[key] as line, x, y
FROM OPENJSON(@multipolygon, '$.coordinates') as polygons
       CROSS APPLY OPENJSON(polygons.value) as lines
              CROSS APPLY OPENJSON(lines.value)
                     WITH (x float '$[0]', y float '$[1]')