PostGreSql

本文主要介绍如何在PostGreSql中提取出jsonb类型字段中的某个key的值

参考：https://www.cnblogs.com/mywebnumber/p/5551092.html

一、简单模式

1. 只有一个{}

   # rule_config 字段格式
   {
     "cardType": 1,
     "sellPrice": null,
     "originPrice": 15
   }
   
   # 获取cardType
   SELECT
       rule_config -> 'cardType' AS cardType 
   FROM
       t_free_ride_card_rule_config 
   WHERE
       title = '测试0211'

   　　
2. 只有一个[]

   # rule_config字段格式
   [
     "zero",
     "one",
     "two"
   ]
   
   # 获取第一个元素
   SELECT
       rule_config ->0  AS cardType 
   FROM
       t_free_ride_card_rule_config 
   WHERE
       title = '测试0211'

3. 两个{}并列

   # rule_config字段格式
   [
     {
       "ruleGuid": "1125720873758932994",
       "mcardType": 1,
       "packStart": "2020-02-14",
       
     },
     {
       "ruleGuid": "1073055433702576129",
       "mcardType": 1,
       "packExpire": "2020-02-18"
     }
   ]
   
   # 获取key为ruleGuid 和 ruleGuid 的值
   SELECT
       json_array_elements ( rule_config :: json ) -> 'ruleGuid' AS ruleGuid,
       json_array_elements ( rule_config :: json ) -> 'mcardType' AS mcardType 
   FROM
       t_free_ride_card_rule_config 
   WHERE
       title = '测试0211'

二、复杂格式

• jsonb数据格式如下

  [
    {
      "platform": 0,
      "cardPackage": [
        {
          "ruleGuid": "1125720873758932994",
          "mcardType": 1,
          "packStart": "2020-02-14",
          "packExpire": "2020-02-15"
        },
        {
          "ruleGuid": "1073055433702576129",
          "mcardType": 1,
          "packStart": "2020-02-16",
          "packExpire": "2020-02-18"
        }
      ],
      "platformExpire": "2020-02-18"
    }
  ]

• 获取相关字段的sql

  # 第一种，嵌套sql
  SELECT
      bottom :: json ->> 'ruleGuid' AS ruleGuid 
  FROM
      (
      SELECT
          json_array_elements ( cardPackage ) AS bottom 
      FROM
          ( SELECT expire_info :: json -> 'cardPackage' AS cardPackage FROM ( SELECT expire_info :: json -> 0 AS expire_info FROM t_ev_month_card WHERE user_new_id = '1200107139' ) AS A ) AS B 
      ) AS F
  
  说明：
  第一层sql：SELECT expire_info :: json -> 0 AS expire_info FROM t_ev_month_card WHERE user_new_id = '1200107139' 获取到最外层1个{}的数据，命名为expire_info列
  第二层sql：从最外层花括号里expire_info获取到 key = “cardPackage” 的内容 expire_info :: json -> 'cardPackage' ，命名为 cardPackage列
  第三层sql：将cardPackage列的内容分为单独的{}
  第四层sql：从每个单独的{}中取出ruleGuid字段（见 一、（1）节）

  
  # 第二种，
  SELECT (json_array_elements((expire_info -> 0):: json ->'cardPackage'))->'ruleGuid' AS a
  FROM t_ev_month_card WHERE user_new_id = '1200107139'
  

   如果数据类型是jsonb，也可以将json替换成jsonb:

　　

SELECT
    bottom :: jsonb -> 'ruleGuid' AS ruleGuid 
FROM
    (
    SELECT
        jsonb_array_elements ( cardPackage ) AS bottom 
    FROM
        (
        SELECT
            expire_info :: jsonb -> 'cardPackage' AS cardPackage 
        FROM
            (
            SELECT
                expire_info :: jsonb -> 0 AS expire_info 
            FROM
                t_ev_month_card 
            WHERE
                user_new_id = '1200107139' 
            ) AS A 
        ) AS B 
    ) AS F