我有一个Postgresql表,其中一个名为“food”的json列。
以下是一些行的示例:
food
["cheese", "salmon", "eggs"]
["salmon", "cheese", "eggs"]
["broccoli", "ham", "milk"]
["salmon", "cheese", "eggs", "pizza"]
目前的结果:
food count
["cheese", "salmon", "eggs"] | 1
["salmon", "cheese", "eggs"] | 1
["broccoli", "ham", "milk"] | 1
["salmon", "cheese", "eggs", "pizza"] | 1
期望的结果:
food count
["cheese", "salmon", "eggs"] | 2
["broccoli", "ham", "milk"] | 1
["salmon", "cheese", "eggs", "pizza"] | 1
有没有办法在不考虑元素顺序的情况下对一个json字段的内容进行GROUP BY?如果两行具有相同的确切内容,那么我希望它们组合在一起。
我的计划是GROUP BY json_array_elements(食物),但由于某种原因,这只返回每行的第一个元素。
实际上类似于@Scoots的答案,但没有排序,窗口,aso:
SELECT (
SELECT jsonb_agg(items order by items)
FROM jsonb_array_elements(food) AS items
) AS food,
count(*)
FROM test_json_grouping
GROUP BY 1;
...解释:
QUERY PLAN
------------------------------------------------------------------------------------------------------
HashAggregate (cost=1635.60..1890.60 rows=200 width=40)
Group Key: (SubPlan 1)
-> Seq Scan on test_json_grouping (cost=0.00..1629.25 rows=1270 width=32)
SubPlan 1
-> Aggregate (cost=1.25..1.26 rows=1 width=32)
-> Function Scan on jsonb_array_elements items (cost=0.00..1.00 rows=100 width=32)
(6 rows)
结果:
food | count
---------------------------------------+-------
["cheese", "eggs", "salmon"] | 2
["broccoli", "ham", "milk"] | 1
["cheese", "eggs", "pizza", "salmon"] | 1
(3 rows)
不直接 - 对于Postgres他们是不同的字符串。
然而,我们可以做的是通过json_array_elements
解压缩这些json字符串,然后使用json_agg
应用我们自己的排序重新打包它们。然后通过工作将它们同化为你的小组。
这是一个查询,说明我的意思:
select
__food.food::text,
count(1)
from (
select
json_agg(_unpack.food order by _unpack.food::text asc) as food
from (
select
row_number() over(),
json_array_elements(food) as food
from
YOUR_SCHEMA.YOUR_FOOD_TABLE
) as _unpack
group by
_unpack.row_number
) as __food
group by
__food.food::text