在 postgres 表中计算不为空的 json 键-> 值

Posted 2023-03-14

【中文标题】在 postgres 表中计算不为空的 json 键-> 值

【英文标题】：Count not null json key->values in postgres table

【发布时间】：2020-06-21 02:14:20

【问题描述】：

我有一个带有字段要求（json 字段）的 postgres 表。我需要计算 json 中的非空键。最好的方法是什么？目前我是这样查询的

select COALESCE(t_count,0) + COALESCE(p_count,0) as total_count from (select
CASE
  WHEN requirements->'FRIDGE_SHELF_SPACE'->'order_frequency' is not null then 1
  ELSE 0
 END as t_count,
CASE
  WHEN requirements->'SUPPLY_CHAIN'->'supply_chain_need' is not null then 1
  ELSE 0
END as p_count
from business_requirements where user_id=3561) as t

仅供参考，整个 json（在需求字段中）看起来像这样

  "FRIDGE_SHELF_SPACE": 
    "order_frequency": 
      "question": "How frequently will you be reordering stock?",
      "answer": "Weekly reordering"
    ,
    "units_per_order": 
      "question": "What is your estimated number of units per order?",
      "answer": "10 - 20"
    
  ,
  "Rational_TAP_LINES": 

  ,
  "PERMANENT_TAP_LINES": 

  ,
  "SUPPLY_CHAIN": 
    "supply_chain_need": 
      "question": "What is your supply chain need?",
      "answer": "Brewing ingredients"
    ,
    "supply_chain_requirements": 
      "question": "Select any of the following requirements (leave blank if not applicable)",
      "answer": [
        "Malt",
        "Yeast"
      ]
    
  ,
  "RESEARCH": 

  

【参考方案1】：

您可以使用 postgres json_each 函数来计算键数：

select count(key) from json_each('
  "FRIDGE_SHELF_SPACE": 
    "order_frequency": 
      "question": "How frequently will you be reordering stock?",
      "answer": "Weekly reordering"
    ,
    "units_per_order": 
      "question": "What is your estimated number of units per order?",
      "answer": "10 - 20"
    
  ,
  "Rational_TAP_LINES": 

  ,
  "PERMANENT_TAP_LINES": 

  ,
  "SUPPLY_CHAIN": 
    "supply_chain_need": 
      "question": "What is your supply chain need?",
      "answer": "Brewing ingredients"
    ,
    "supply_chain_requirements": 
      "question": "Select any of the following requirements (leave blank if not applicable)",
      "answer": [
        "Malt",
        "Yeast"
      ]
    
  ,
  "RESEARCH": 

  
') where exists (select 1 from json_each(value) s);

希望这会对你有所帮助:) 祝你好运

【讨论】：

谢谢贾斯宾德。真的很有帮助。