Querying array of nested objects with nested array of objects in Redshift

Question

Let's say I have the following JSON

```json
{
  "id": 1,
  "sets": [
    {
      "values": [
        {
          "value": 1
        },
        {
          "value": 2
        }
      ]
    },
    {
      "values": [
        {
          "value": 5
        },
        {
          "value": 6
        }
      ]
    }
  ]
}
```

If the table name is `X` I expect the query

```sql
 SELECT x.id, v.value 
 FROM X as x,
   x.sets as sets,
   sets.values as v
```

to give me

```
id, value
1, 1
1, 2
2, 5
2, 6
```

and it does work if both sets and values has **one** object each. When there's more the query fails with column 'id' had 0 remaining values but expected 2. Seems to me I'm not iterating over "sets" properly?

So my question is: what's the proper way to query data structured like my example above in Redshift (using PartiQL)?

Answer

Hi rakibansary,

Unless I'm wrong, I cannot see the name of the SUPER datatype column in your query. In the following example, my SUPER datatype column, where the JSON record is stored, is called *json_text*.

```
 SELECT x.json_text.id, v.value 
 FROM X as x,
   x.json_text.sets as sets,
   sets.values as v
```
Thanks,

Answer

Hi rakibansary,

The *json_text* column is just an example to show you how usually PartiQL is used on SUPER datatype columns.

SUPER datatype is used for semi-structured data such as JSON. The following link contains several examples on querying semi-structured data https://docs.aws.amazon.com/redshift/latest/dg/query-super.html#navigation.

If you are having a Parquet file with several columns and a json column, then you can use the SERIEALIZETOJSON option while copying the data to Redshift. You can find an example on the following link (the *Copying data from columnar-format Parquet and ORC* section) https://docs.aws.amazon.com/redshift/latest/dg/ingest-super.html#copy_json.

Thanks,

Querying array of nested objects with nested array of objects in Redshift

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