Arrays 使用PostgreSQL从JSON提取到多列
我有一个列Arrays 使用PostgreSQL从JSON提取到多列,arrays,json,postgresql,select,postgresql-9.6,Arrays,Json,Postgresql,Select,Postgresql 9.6,我有一个列item_id,其中包含JSON(like?)结构中的数据 +----------+---------------------------------------------------------------------------------------------------------------------------------------+ | id |
item_id
,其中包含JSON(like?)结构中的数据
+----------+---------------------------------------------------------------------------------------------------------------------------------------+
| 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"]}" |
+----------+---------------------------------------------------------------------------------------------------------------------------------------+
我需要每个逗号前的最后四位数字(如果有),最后四位数字要区分并分隔成单独的列。distinct也应该在
id
之间发生,因此只允许一个id为57638的结果行
下面是一个代码草案,它没有给出正确的答案。
预期结果应如下所示:
+----------+-----------+-----------+
| id | item_id_1 | item_id_2 |
+----------+-----------+-----------+
| 56711 | 1974 | |
| 56712 | 4220 | 4221 |
| 56721 | 1356 | |
| 56722 | 3349 | |
| 57638 | 3364 | 3365 |
+----------+-----------+-----------+
结果中可能有很多“item\u id\u%”列。您可以取消json数组的测试,将每个元素的最后4个字符作为一个数字,然后进行条件聚合:
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
您可以向外部查询添加更多的条件max()
s,以处理更多可能的值
:
id | item_id_1 | item_id_1
----: | --------: | --------:
56711 | 1974 | null
56712 | 4220 | 4221
56721 | 1356 | null
56722 | 3349 | null
57638 | 3364 | 3365
id |项目id |项目id | 1
----: | --------: | --------:
56711 | 1974 |无效
56712 | 4220 | 4221
56721 | 1356 |空
56722 | 3349 |空
57638 | 3364 | 3365
您可以卸载json数组,将每个元素的最后4个字符作为一个数字,然后执行条件聚合:
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
您可以向外部查询添加更多的条件max()
s,以处理更多可能的值
:
id | item_id_1 | item_id_1
----: | --------: | --------:
56711 | 1974 | null
56712 | 4220 | 4221
56721 | 1356 | null
56722 | 3349 | null
57638 | 3364 | 3365
id |项目id |项目id | 1
----: | --------: | --------:
56711 | 1974 |无效
56712 | 4220 | 4221
56721 | 1356 |空
56722 | 3349 |空
57638 | 3364 | 3365
由于您无法动态选择列(您不知道将有多少个项目\u id\u X),我认为您应该使用unpivot/pivot,请参阅此处的示例,因为您无法动态选择列(您不知道将有多少个项目\u id\u X),我认为您应该使用unpivot/pivot,请参阅此处的示例