用postgres檢查json數組

Question

我在postgres中有一個遵循以下格式的JSONB數組。

{
   "id" : 22323,
   "details" : [
                        {
                            "status" : "stage1",
                             "timestamp" : "2017-09-89"
                         },
                        {
                            "status" : "stage2",
                             "timestamp" : "2017-09-89"
                         }
                        ]
    }

我需要在stage2中獲取時間戳，如何在postgresql中選擇特定狀態的時間戳？

Answer 1

如果“ details”的索引始終與“ status”：“ stageVALUE的索引相同，則可以使用-> element，但是如果不這樣，則需要使用json_array_elements遍歷array的元素，例如：

t=# with b as (with v as (select '{
   "id" : 22323,
   "details" : [
                        {
                            "status" : "stage1",
                             "timestamp" : "2017-09-89"
                         },
                        {
                            "status" : "stage2",
                             "timestamp" : "2017-09-89"
                         }
                        ]
    }'::json j)
select json_array_elements(j->'details') j from v)
select j->>'timestamp' from b where j->>'status' = 'stage2'
;
  ?column?
------------
 2017-09-89
(1 row)

並且如果stage2始終是第二個數組元素，則便宜一些：

t=# with v as (select '{
   "id" : 22323,
   "details" : [
                        {
                            "status" : "stage1",
                             "timestamp" : "2017-09-89"
                         },
                        {
                            "status" : "stage2",
                             "timestamp" : "2017-09-89"
                         }
                        ]
    }'::json j)
select j->'details'->1->>'timestamp' from v;
  ?column?
------------
 2017-09-89
(1 row)

我使用索引1 cos數組從0開始索引