在 Snowflake 中，如何解析未命名的 JSON 数组并使用键值而不是数组切片方法访问每个键？

Question

I have a JSON array in Snowflake, where I need to parse into a table, ie, convert all information into a row. Assume my table includes two columns: id and json_tag column.

An example row is as below:

{ [
json_tag

[
  {
    "key": "app.name",
    "value": "myapp1"
  },
  {
    "key": "device.name",
    "value": "myiPhone11"
  },
  {
    "key": "iOS.dist",
    "value": "latestDist5"
  }
]

This is not a standard example, another example can have 5 or even 6 with new key names. An example is below:

{ [
json_tag

[
  {
    "key": "app.name",
    "value": "myapp2"
  },
  {
    "key": "app.cost",
    "value": "$2.99"
  },
  {
    "key": "device.name",
    "value": "myiPhoneX"
  },
  {
    "key": "device.color",
    "value": "gold"
  },
  {
    "key": "iOS.dist",
    "value": "latestDist4.9"
  }
]

What I want is working on a table (without creating a new one) where the json row is split into columns as below:

id app.name app.cost device.name device.color iOS.dist 
1  myapp1   null     myiPhone11  null         latestDist5
2  myapp2   $2.99    myiPhoneX   gold         latestDist4.9

I tried the following snippet:

with parsed_tb as (
    select id, 
           to_variant(parse_json(json_tag)) as parsed_json_tag
    from mytable
)



 select parsed_json_tag[0]:value::varchar as app_name, 
        parsed_json_tag[1]:value::varchar as app_cost, 
        parsed_json_tag[2]:value::varchar as device_name
 from tb; 

As you can imagine, the snippet above does not work when there is no app.cost in key values or every row differs in number of keys and values.

I tried lateral flatten command in Snowflake, but out creates many rows and I cannot figure out how to put them in columns in the same row. I also tried using recursive command, and could not achieve it.

So my question is:

1. How can I access a key by its name rather than slicing an array as I do above? - this would solve my problem I guess.

2. If #1 solution I imagine does not fix, how can I attain the table above?

Answer 1

I have found a solution to this problem with the help of following thread:

Mysql, reshape data from long / tall to wide

Solution is first parsing json column with unique identifier, and then lateral flattening and then grouping the results by unique identifier [formatting table from long to wide as given in the link above].

So for the examples I provided above, the solution would be as follows:

with tb as (
     select id, 
            to_variant(parse_json(json_tags)) as parsed_json_tags
     from mytable
), 

flattened as (
     select id,
            VALUE:value::string as value, 
            VALUE:key::string as key
     from mytable, lateral flatten(input => (tb.parsed_json_tags))
)

select id, 
       MAX( IFF( key='app.name', value, NULL ) ) AS app_name,
       MAX( IFF( key='app.cost', value, NULL ) ) AS app_cost,
       MAX( IFF( key='device.name', value, NULL ) ) AS device_name,
       MAX( IFF( key='device.color', value, NULL ) ) AS device_color,
       MAX( IFF( key='iOS.dist', value, NULL ) ) AS ios_dist

from flattened
group by 1;