返回 Postgres 嵌套 JSON 数组

Question

我一直在四处寻找这个问题的答案，但没有找到足够接近我所寻找的答案。

我有两个表：

CREATE TABLE skill_tree (
    ID SERIAL PRIMARY KEY,
    NAME TEXT NOT NULL,
    DESCRIPTION TEXT NOT NULL
);

和

CREATE TABLE skill (
    ID SERIAL PRIMARY KEY,
    NAME TEXT NOT NULL,
    DESCRIPTION TEXT NOT NULL,
    DURATION INTEGER NOT NULL,
    COOLDOWN INTEGER NOT NULL,
    SKILL_TREE_ID SERIAL REFERENCES skill_tree(id)
);

我正在尝试从我的 Postgres 数据库中 return JSON，其结构如下：

[{
    "id": 1,
    "name": "skill tree 1",
    "description": "skill tree description",
    "skills": [{
        "id": 1,
        "name": "skill 1",
        "description": "skill 1 desc",
        "duration": 10,
        "cooldown": 20
    }, {
        "id": 2,
        "name": "skill 2",
        "description": "skill 2 desc",
        "duration": 20,
        "cooldown": 30
    }]
}]

我能够从这里得到类似的东西但除了技能名称之外无法检索到任何东西。

Answer 1

table skill 应该是这样的：

CREATE TABLE skill (
    ID SERIAL PRIMARY KEY,
    NAME TEXT NOT NULL,
    DESCRIPTION TEXT NOT NULL,
    DURATION INTEGER NOT NULL,
    COOLDOWN INTEGER NOT NULL,
    SKILL_TREE_ID INTEGER REFERENCES skill_tree(id) -- cannot be serial!
);

使用 jsonb_build_object() 和 jsonb_agg()。请注意，查询在某种程度上类似于预期的对象。

select jsonb_pretty(jsonb_agg(js_object)) result
from (
    select 
        jsonb_build_object(
            'id', id, 
            'name', name, 
            'description', description, 
            'skills', jsonb_agg(skill)
        ) js_object
    from (
        select 
            t.*, 
            jsonb_build_object(
                'id', s.id, 
                'name', s.name, 
                'description', s.description, 
                'duration', duration, 
                'cooldown', cooldown
            ) skill
        from skill_tree t
        join skill s on s.skill_tree_id = t.id
        ) s
    group by id, name, description
    ) s;

我用 jsonb_pretty() 包装了结果以获得不错的输出：

                     result                      
-------------------------------------------------
 [                                              +
     {                                          +
         "id": 1,                               +
         "name": "skill tree 1",                +
         "skills": [                            +
             {                                  +
                 "id": 1,                       +
                 "name": "skill 1",             +
                 "cooldown": 20,                +
                 "duration": 10,                +
                 "description": "skill 1 desc"  +
             },                                 +
             {                                  +
                 "id": 2,                       +
                 "name": "skill 2",             +
                 "cooldown": 30,                +
                 "duration": 30,                +
                 "description": "skill 2 desc"  +
             }                                  +
         ],                                     +
         "description": "skill tree description"+
     }                                          +
 ]

请注意，json 对象的元素顺序未定义。

返回 Postgres 嵌套 JSON 数组

Returning Postgres Nested JSON Array

arrays

postgresql

json

jsonb