Question

我的表名为doc_definition，其json列definition的格式如下：

[{
  "id":"0",
  "name:"Ques1"
 },{
  "id":"1",
  "name:"Ques2"
 },{
  "id":"2",
  "name:"Ques3"
}]

另一个表doc，其中包含另一个json列def_val，其格式为：

{
  "0":{
       "value":"Ans1"
      },
  "1":{
       "value":"Ans2"
      },
  "2":{
       "value":"Ans3"
      }
}

我想创建一个Postgres SQL查询，通过匹配两个json中的id字段来提供相应问题的值。到目前为止，我已经想出了这个：

SELECT json_array_elements(def.definition) ->> 'name' AS json_test
FROM document_definitions AS def
INNER JOIN documents AS doc 
    ON doc.document_definition_id = def.id
WHERE doc.id = 892 AND json_array_elements(def.definition) ->> 'name' = 'Ques2'

但这引发了异常：

ERROR:  argument of AND must not return a set

当我将json_array_elements(def.definition) ->> 'name' = 'Ques2'放入SELECT子句时，它返回布尔值。

我当时不知道什么是错的。 Plz帮助？

Answer 1

该查询怎么样：

SELECT json_array_elements(def.definition) ->> 'name' AS json_test
FROM document_definitions AS def
INNER JOIN documents AS doc 
    ON doc.document_definition_id = def.id
WHERE doc.id = 892 AND (json_array_elements(def.definition) ::json->> 'name') = 'Ques2'

Answer 2

经过多次试验和错误，我已经想出了这个。如果我能以任何方式改善这一点，请告诉我。

SELECT definition_json.definition_value -> definition_json.def_value_id ->> 'value' AS definition_value
FROM (
    SELECT json_array_elements(def.definition) ->> 'name' = 'Ques2' AS is_definition_present,
        json_array_elements(def.definition) ->> 'id' AS def_value_id,
        doc.definition_value, doc.id AS document_id, def.id AS definition_id
    FROM document_definitions AS def
    INNER JOIN documents AS doc 
        ON doc.document_definition_id = def.id
    ) AS definition_json
WHERE definition_json.is_definition_present = 't' AND definition_json.document_id = 892

如何从两个不同的表中查询JSON数组？

2 个答案: