[英]Postgres: row with comma separated value to array of json objects
Using postgres 9.4. 使用Postgres 9.4。
Data: 数据:
+-----+------+
| id | type |
+-----+------+
| 1 | A |
+-----+------+
| 2,3 | A |
+-----+------+
| 4 | B |
+-----+------+
Desired output (JSON): 所需的输出(JSON):
[
[{"id": "1", "type": "A"}],
[{"id": "2", "type": "A"},{"id": "3", "type": "A"}],
[{"id": "4", "type": "B"}]
]
I've tried: 我试过了:
SELECT array_to_json(array_agg(c))
FROM
(
SELECT
regexp_split_to_table(id, ',') AS id,
type
FROM my_table
) c;
which gets me to a simple array of json objects: 这使我进入一个简单的json对象数组:
[
{"id": "1", "type": "A"},
{"id": "2", "type": "A"},
{"id": "3", "type": "A"},
{"id": "4", "type": "B"}]
]
How do I wrap each resultset (not each row) of the subquery in an array? 如何将子查询的每个结果集(而不是每一行)包装在数组中?
I believe this does what you want: 我相信这可以满足您的需求:
with t as (
select *
from (values ('1', 'A'), ('2,3', 'A'), ('4', 'B')) v(ids, type)
)
select json_agg(c)
from (select array_to_json(array_agg( json_build_object('id', c.id, 'type', c.type))) as c
from (select ids, regexp_split_to_table(ids, ',') AS id, type
from t
) c
group by ids
) i;
You can create the JSON value for a single row using: 您可以使用以下方法为单行创建JSON值:
select (select json_agg(to_json(t))
from (
select i.id, t.type
from unnest(string_to_array(t.ids, ',')
) as i(id)) t) json_id
from the_table t
you can wrap that into a derived table to aggregate everything to a single JSON value: 您可以将其包装到派生表中,以将所有内容聚合为一个JSON值:
select json_agg(json_id)
from (
select (select json_agg(to_json(t))
from (select i.id, t.type from unnest(string_to_array(t.ids, ',')) as i(id)) t) json_id
from the_table t
) x;
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