PostgreSQL 聚合 json 个数组

Question

我看到很多关于使用 json_array_elements 提取 JSON 数组元素的参考资料。但是，这似乎只适用于 1 个阵列。如果我在通用查询中使用它，我会得到错误

ERROR: cannot call json_array_elements on a scalar

给出这样的东西：

orders
{ "order_id":"2", "items": [{"name": "apple","price": 1.10}]}
{ "order_id": "3","items": [{"name": "apple","price": 1.10},{"name": "banana","price": 0.99}]}

我要提取

item	count
apple	2
banana	1

或

item	total_value_sold
apple	2.20
banana	0.99

是否可以使用 json_array_elements 聚合 json 个数组？

Answer 1

使用orders->'items'的函数来拉平数据：

select elem->>'name' as name, (elem->>'price')::numeric as price
from my_table
cross join jsonb_array_elements(orders->'items') as elem;

很容易从扁平化的数据中得到你想要的聚合：

select name, count(*), sum(price) as total_value_sold
from (
    select elem->>'name' as name, (elem->>'price')::numeric as price
    from my_table
    cross join jsonb_array_elements(orders->'items') as elem
    ) s
group by name;

Db<>fiddle.

PostgreSQL 聚合 json 个数组

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