json - 雪花中有条件横向展平

Question

我有一个包含 json variant 的表，其中包含可能存在也可能不存在的键，具体取决于 API 响应。

示例表:

create or replace temporary table test (variant_col variant);

insert into test(variant_col)
select parse_json('{"response": [{"key1":[1,2,3]}, {"key2":[7,8,9]}]}');
insert into test(variant_col)
select parse_json('{"response": [{"key2":[7,8,9]}]}');

我想根据它们的键横向展平它们，并使用key1(如果存在)，否则使用key2(它将始终存在)

SELECT
    iff(f2.value::int is null, 'key2', 'key1') as value_type,
    ifnull(f2.value::int, f3.value::int) as desired_value
FROM
    test,
    LATERAL FLATTEN(input => response) as f1,
    LATERAL FLATTEN(input => f1.value:key1) as f2,
    LATERAL FLATTEN(input => f1.value:key2) as f3
;

Answer 1

我们可以通过为每一行提供一个 id 来解决这个问题，然后我们可以联合 2 个查询的结果 - 取决于 key1 是否存在:

with data as (
    select row_number() over(order by 0) id, * 
    from test
), rows_with_key1 as (
    select data.*, value v
    from data
        , lateral flatten(input => variant_col:response) as f1
    where f1.value:key1 is not null
), rows_without_key1 as (
    select data.*, value v
    from data
        , lateral flatten(input => variant_col:response) as f1
    where id not in (select id from rows_with_key1)
)


select id, value, variant_col
from rows_with_key1
    , lateral flatten(input => v:key1) ff
union all
select id, value, variant_col
from rows_without_key1
    , lateral flatten(input => v:key2)
;