[英]Postgres: row with comma separated value to array of json objects
使用Postgres 9.4。
數據:
+-----+------+
| id | type |
+-----+------+
| 1 | A |
+-----+------+
| 2,3 | A |
+-----+------+
| 4 | B |
+-----+------+
所需的輸出(JSON):
[
[{"id": "1", "type": "A"}],
[{"id": "2", "type": "A"},{"id": "3", "type": "A"}],
[{"id": "4", "type": "B"}]
]
我試過了:
SELECT array_to_json(array_agg(c))
FROM
(
SELECT
regexp_split_to_table(id, ',') AS id,
type
FROM my_table
) c;
這使我進入一個簡單的json對象數組:
[
{"id": "1", "type": "A"},
{"id": "2", "type": "A"},
{"id": "3", "type": "A"},
{"id": "4", "type": "B"}]
]
如何將子查詢的每個結果集(而不是每一行)包裝在數組中?
我相信這可以滿足您的需求:
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;
這是db <>小提琴。
您可以使用以下方法為單行創建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
您可以將其包裝到派生表中,以將所有內容聚合為一個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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