如何使用mysql查询将mysql关系联接表数据转换为json数据

Question

我有以下三个关系表，例如Country，Stare和City。当我在下面查询城市数组多次触发时，我想从关系数据表中以Json格式获取这些。我想获取以下格式的JSON合并数据。

select JSON_OBJECT('country_id',b.country_id, 'country_name', a.country_name, 'stateList',JSON_ARRAYAGG( JSON_OBJECT('cityList',(select JSON_ARRAYAGG(x.city_name) FROM city x where x.city_id_mapping=b.state_id  group by x.state_id_mapping),'stateid',b.state_id,'state_name',b.state_name))) 
FROM State b,Country a , City c where a.country_id=b.state_id and b.state_id=c.city_id by a.country_Id order by a.country_Id;

国家/地区：

County_id       country_name        currency  
-----------------------------------------------------!

1                    India           Rs.
2                    USA             Doller
3                    NL              Euro 

状态：

State id     Stare name          language         country_maping_id
-------------------------------------------------------------------!
1            Maharashtra          Marathi           1
2            WB                   Bengali           1
3            TN                   Tamil             1
4            New York             English           2
5            Washington           English           2
6            Amsterdam            Duch              3

城市：

City id               City Name               state id
---------------------------------------------------------!
1                        Mumbai                    1
2                        Thane                     1
3                        Nagpur                    1
4                        Kolkata                   2
5                        Asansol                   2
6                        Siliguri                  3
7                       Tacoma                     5
8                        Olmpia                    5

想要获取JSON格式的合并数据，如下所示

[{
            countryId: "1", countryName: “India”,
            subgrouplist:
                [{
                    State_id: "1", State_name: " Maharashtra ", language  : " Marathi ",
                    city: ["Mumbai ", " Thane ", " Nagpur"]
                },
                {
                    State_id: "2", State_name: "WB", language  : "Bengali",
                    city: ["Kolkata", " Asansol", " Siliguri"]
                },]         
        },
    {
            countryId: "2", countryName: 'USA’,
            subgrouplist:
                [{
                    State_id: "1", State_name: " New York ", language  : “English",
                    city: []
                },
                {
                    State_id: "1", State_name: "Washington", language  : "English",
                    city: ["Tacoma”,”Olmpia "]
                },


]},
    {countryId: "1", countryName: 'NL',
            subgrouplist:
                [{
                   State_id:, State_name: , language  : ,
                    city: []
                }           
]},]