[英]Extract into multiple columns from JSON with PostgreSQL
我有一列item_id
包含 JSON (像?)結構中的數據。
+----------+---------------------------------------------------------------------------------------------------------------------------------------+
| id | item_id |
+----------+---------------------------------------------------------------------------------------------------------------------------------------+
| 56711 | {itemID":["0530#2#1974","0538\/2#2#1974","0538\/3#2#1974","0538\/18#2#1974","0539#2#1974"]}" |
| 56712 | {itemID":["0138528#2#4221","0138529#2#4221","0138530#2#4221","0138539#2#4221","0118623\/2#2#4220"]}" |
| 56721 | {itemID":["2704\/1#1#1356"]}" |
| 56722 | {itemID":["0825\/2#2#3349","0840#2#3349","0844\/10#2#3349","0844\/11#2#3349","0844\/13#2#3349","0844\/14#2#3349","0844\/15#2#3349"]}" |
| 57638 | {itemID":["0161\/1#2#3364","0162\/1#2#3364","0163\/2#2#3364"]}" |
| 57638 | {itemID":["109#1#3364","110\/1#1#3364"]}" |
+----------+---------------------------------------------------------------------------------------------------------------------------------------+
我需要每個逗號之前的最后四位數字(如果有),最后 4 位數字被區分並分成單獨的列。
distinct 也應該發生在id
上,因此只允許一個 id: 57638 的結果行。
這是一個沒有給出正確答案的代碼草案。 所需的結果應如下所示:
+----------+-----------+-----------+
| id | item_id_1 | item_id_2 |
+----------+-----------+-----------+
| 56711 | 1974 | |
| 56712 | 4220 | 4221 |
| 56721 | 1356 | |
| 56722 | 3349 | |
| 57638 | 3364 | 3365 |
+----------+-----------+-----------+
結果中可能有很多“item_id_%”列。
您可以取消嵌套 json 數組,獲取每個元素的最后 4 個字符作為數字,然后進行條件聚合:
select
id,
max(val) filter(where rn = 1) item_id_1,
max(val) filter(where rn = 2) item_id_2
from (
select
id,
right(val, 4)::int val,
dense_rank() over(partition by id order by right(val, 4)::int) rn
from mytable t
cross join lateral jsonb_array_elements_text(t.item_id -> 'itemID') as x(val)
) t
group by id
您可以向外部查詢添加更多條件max()
以處理更多可能的值。
id | item_id_1 | item_id_1 ----: | --------: | --------: 56711 | 1974 | null 56712 | 4220 | 4221 56721 | 1356 | null 56722 | 3349 | null 57638 | 3364 | 3365
with the_table (id, item_id) as (
values
(56711, '{"itemID":["0530#2#1974","0538\/2#2#1974","0538\/3#2#1974","0538\/18#2#1974","0539#2#1974"]}'),
(56712, '{"itemID":["0138528#2#4221","0138529#2#4221","0138530#2#4221","0138539#2#4221","0118623\/2#2#4220"]}'),
(56721, '{"itemID":["2704\/1#1#1356"]}'),
(56722, '{"itemID":["0825\/2#2#3349","0840#2#3349","0844\/10#2#3349","0844\/11#2#3349","0844\/13#2#3349","0844\/14#2#3349","0844\/15#2#3349"]}'),
(57638, '{"itemID":["0161\/1#2#3364","0162\/1#2#3364","0163\/2#2#3364"]}'),
(57638, '{"itemID":["109#1#3365","110\/1#1#3365"]}')
)
select id
,(array_agg(itemid)) [1] itemid_1
,(array_agg(itemid)) [2] itemid_2
from (
select distinct id
,split_part(replace(json_array_elements(item_id::json -> 'itemID')::text, '"', ''), '#', 3)::int itemid
from the_table
order by 1
,2
) t
group by id
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