mysql使用CONCAT、GROUP_CONCAT嵌套查询出json格式数据

tb_factory表由 factory_code 和 factory_name 字段，查询出如下所示效果：

{ "factory_0001": "工厂1", "factory_0002": "工厂2", ... }

select sql：

SELECT CONCAT( "{", GROUP_CONCAT( CONCAT( CONCAT( "\"",factory_code,"\"" ), ":", CONCAT( "\"",factory_name,"\"" ) ) SEPARATOR ',' ), "}" ) AS factory_codes FROM tb_factory