arrays - 如何在postgresql中提取json数组元素

Question

我想做的是将 29.0 和 34.65 相加并按 P_id 分组

Table: transaction_items
Column name: Debits, P_id
Column data type: text, text

数据:

---

借记

[{"amount":29.0,"description":"Fee_Type_1"}
[{"amount":"34.65","description":"Fee_Type_1"}

---

P_id

16
16

---

我尝试使用此处提到的解决方案 [https://stackoverflow.com/questions/27834482/how-to-get-elements-from-json-array-in-postgresql][1]

select     transaction_line_items.P_id,
           each_attribute ->> 'amount' Rev
from       transaction_line_items
cross join json_array_elements(to_json(Debits)) each_section
cross join json_array_elements(each_section -> 'attributes') each_attribute
where      (each_attribute -> 'amount') is not null;

但是，我收到一条错误消息“无法解构标量”。

有人可以告诉我如何解析我正在寻找的值吗？

谢谢。

Answer 1

看来你的数据坏了。由于缺少右方括号，Debits 列的值不是有效的 json。假设您的数据应如下所示:

[{"amount":29.0,"description":"Fee_Type_1"}]
[{"amount":"34.65","description":"Fee_Type_1"}]

下面的查询做你想做的:

select p_id, sum(amount)
from (
    select p_id, (elements->>'amount')::numeric amount
    from transaction_items
    cross join json_array_elements(debits::json) elements
    ) sub
group by p_id;