Question

我们在表party_procedures

中有一个json列'passed_states_data'

列数据如下所示：

[{“state”：“documents”，“passed_at”：“2016-02-04 13:16:51 +0100“}，{”state“：”problems“，”passed_at“：”2016-02-04 16:10:07 +0100“}，{”state“：”waiting_for_physical_documents“，”passed_at“：”2016- 02-08 十三时五十分17秒 +0100“}，{”state“：”customer_acceptance“，”passed_at“：”2016-02-08 13:50:19 +0100“}，{”state“：”customer_identifier“，”passed_at“：”2016-02-08 13:50:54 +0100“}，{”state“：”checking_account“，”passed_at“：”2016- 02-08 13时51分45秒 0100 “}，{” 状态 “：” transfer_money_to_savings_account “ ”passed_at“：” 2016年2月10日 09:12:18 +0100“}]

我需要构建只返回存在'transfer_money_to_savings_account'的行的查询，然后获取pass_at日期。

所以查询应该返回如下内容：

select blah as "date passed" from party_procedures pp
  where json_array_elements(pp.passed_states_data)->>'state'='transfer_money_to_savings_account' = 't'

或类似的东西。

Answer 1

json_array_elements()函数返回 json 集合，因此，您无法使用->>;换句话说，您需要迭代json数组元素集并检查state是否具有您要查找的值。

WITH t(passed_states_data) AS ( VALUES
  ('[{"state":"documents","passed_at":"2016-02-04 13:16:51 +0100"},
     {"state":"problems","passed_at":"2016-02-04 16:10:07 +0100"},
     {"state":"waiting_for_physical_documents","passed_at":"2016-02-08 13:50:17 +0100"},
     {"state":"customer_acceptance","passed_at":"2016-02-08 13:50:19 +0100"},
     {"state":"customer_identifier","passed_at":"2016-02-08 13:50:54 +0100"},
     {"state":"checking_account","passed_at":"2016-02-08 13:51:45 +0100"},
     {"state":"transfer_money_to_savings_account","passed_at":"2016-02-10 09:12:18 +0100"}]'::JSON)
)
SELECT j->>'passed_at' as "date passed" FROM t, json_array_elements(t.passed_states_data) j
WHERE j->>'state' = 'transfer_money_to_savings_account';

结果：

        date passed        
---------------------------
 2016-02-10 09:12:18 +0100
(1 row)

如何在postgres中执行此查询？

1 个答案: