根据条件将雪花变体列中的 JSON 值解析为多列

Question

我正在尝试解析表 table_a 中 test_column 列中的以下 JSON 数据。 如果标签部门有Electrical，dept_1应该默认为1，如果标签部门有Electronics，dept_2应该默认为1，如果标签部门有Chemical，dept_3应该默认为1。

测试列
{"labels": {"department_id": "1","department": ["Electrical","Electronics","Chemical"]}}
{"labels": {"department_id": "2","department": ["电气"]}}

我使用了下面的查询，但它没有产生我想要的 -

使用的查询：

select dept_id, 
case when dept='Electrical' then 1 else NULL end as dep1,
case when dept='Electronics' then 2 else NULL end as dep2,
case when dept='Chemical' then 3 else NULL end as dep3
from(
     SELECT 
         test_column:labels:department_id::varchar as dept_id, 
         array_to_string(test_column:labels:department,',') as dept
     FROM table_a
  );

你能告诉我出了什么问题吗？ 对于具有全部 3 个电气、电子和化学的记录，我正在获取 NULL。

预期结果：

部门编号	部门_1	部门_2	部门_3
1	1	1	1
2	1	空值	空值

Answer 1

您有 2 个选项可以以不同的方式执行此操作。

选项#1：展平你的数组，然后重新聚合你的case语句：

WITH x AS (
    SELECT parse_json('{"labels": {"department_id": "1","department": ["Electrical","Electronics","Chemical"]}}') as var
)
SELECT  x.var:labels:department_id::integer as dept_id, 
        max(case when y.value::varchar='Electrical' then 1 else NULL end) as dep1,
        max(case when y.value::varchar='Electronics' then 2 else NULL end) as dep2,
        max(case when y.value::varchar='Chemical' then 3 else NULL end) as dep3
FROM x,
lateral flatten (input=>var:labels:department) y
group by 1;

选项#2 - 因为你的 case 语句只是评估一个值的存在，你可以使用ARRAY_CONTAINS函数查看数组来评估：

WITH x AS (
    SELECT parse_json('{"labels": {"department_id": "1","department": ["Electrical","Electronics","Chemical"]}}') as var
)
SELECT  x.var:labels:department_id::integer as dept_id, 
        case when array_contains('Electrical'::variant, var:labels:department::array) then 1 else NULL end as dep1,
        case when array_contains('Electronics'::variant, var:labels:department::array) then 2 else NULL end as dep2,
        case when array_contains('Chemical'::variant, var:labels:department::array) then 3 else NULL end as dep3
FROM x;

Answer 2

请尝试以下查询：

SELECT 
    test_column:labels:department_id::varchar as dept_id, 
    IFF(ARRAY_CONTAINS('Electrical'::VARIANT, test_column:labels:department), 1, NULL) as DEP_1,
    IFF(ARRAY_CONTAINS('Electronics'::VARIANT, test_column:labels:department), 1, NULL) as DEP_2,
    IFF(ARRAY_CONTAINS('Chemical'::VARIANT, test_column:labels:department), 1, NULL) as DEP_3
FROM table_a;