Question

我的表

validate :checksum_valid?

private
def checksum_valid?
  if number.present?
    errors.add(:number, "is not valid.") unless number_valid?
  end
end

def number_valid?
  number.length < 20 && Luhn.valid?(number)
end

插入：

create table i (a json)

我希望提取2541之后出现的字段。在这种情况下答案为0

查询我的Json：

insert into i values ('[[1300,[{"id":5,"time":1451423706048,"zon":0,"name":"AMighty","loc":"ny"},[[3405,0,1000],[35,0,1000],[3401,0,10000],[2541,0,1000]]]]]' )

它只返回一行。

Answer 1

您需要遍历所有嵌套数组才能获得必要的元素：

WITH i(a) AS ( VALUES
  ('[[1300,[{"id":5,"time":1451423706048,"zon":0,"name":"AMighty","loc":"ny"},[[3405,0,1000],[35,0,1000],[3401,0,10000],[2541,0,1000]]]]]'::JSON)
)
SELECT
  array_element->1->1->3 as array_you_look_for,
  array_element->1->1->3->1 as inner_array_element
FROM i,
  json_array_elements(a) as array_element;

输出：

 array_you_look_for | inner_array_element 
--------------------+---------------------
 [2541,0,1000]      | 0
(1 row)

从JSON数组中提取字段

1 个答案: