我使用flask_sqlalchemy和flask_restless来创建一个API端点来访问PostgreSQL数据库中的数据。如何在flask-restless中构造以下SQL查询?
SELECT AVG("SpeedBand"), "Location"
FROM public.traffic_data
WHERE "RoadName"='ABC ROAD'
GROUP BY "Location"
返回属于" ABC ROAD"的所有坐标对。和每对坐标上的平均速度:
avg | Location
------------------------
1)'1.52' | 'X1 Y1 X2 Y2'
2)'1.85' | 'X3 Y3 X4 Y4'
------------------------
目前,此查询:
http://127.0.0.1:5000/api/traffic_data?q={"filters":[{"name":"RoadName","op":"==","val":"ABC ROAD"}]}
返回属于" ABC ROAD"的所有数据的JSON字符串。以及不同时间的所有速度数据:
{
"num_results": 26,
"objects": [
{
"DateTime": "2017-09-07T19:25:37.035325",
"LinkID": "109002906",
"Location": "X1 Y1 X2 Y2",
"RoadName": "ABC ROAD",
"SpeedBand": 3,
"id": 34094
},
{
"DateTime": "2017-09-07T19:25:37.035325",
"LinkID": "109002907",
"Location": "X3 Y3 X4 Y4",
"RoadName": "ABC ROAD",
"SpeedBand": 1,
"id": 38003
},
{
"DateTime": "2017-09-13T09:57:07.163900",
"LinkID": "109002906",
"Location": "X1 Y1 X2 Y2",
"RoadName": "ABC ROAD",
"SpeedBand": 1,
"id": 92874
},
{
"DateTime": "2017-09-13T09:57:07.163900",
"LinkID": "109002907",
"Location": "X3 Y3 X4 Y4",
"RoadName": "ABC ROAD",
"SpeedBand": 1,
"id": 96783
},
{
"DateTime": "2017-09-13T09:57:07.163900",
"LinkID": "109002906",
"Location": "X1 Y1 X2 Y2",
"RoadName": "ABC ROAD",
"SpeedBand": 1,
"id": 114755
},
{
"DateTime": "2017-09-13T09:57:07.163900",
"LinkID": "109002907",
"Location": "X3 Y3 X4 Y4",
"RoadName": "ABC ROAD",
"SpeedBand": 2,
"id": 114756
},
{
"DateTime": "2017-09-13T10:08:17.727949",
"LinkID": "109002906",
"Location": "X1 Y1 X2 Y2",
"RoadName": "ABC ROAD",
"SpeedBand": 2,
"id": 151654
},
{
"DateTime": "2017-09-13T10:08:17.727949",
"LinkID": "109002907",
"Location": "X3 Y3 X4 Y4",
"RoadName": "ABC ROAD",
"SpeedBand": 2,
"id": 155563
},
{
"DateTime": "2017-09-13T10:19:39.040191",
"LinkID": "109002906",
"Location": "X1 Y1 X2 Y2",
"RoadName": "ABC ROAD",
"SpeedBand": 2,
"id": 210434
},
{
"DateTime": "2017-09-13T10:19:39.040191",
"LinkID": "109002907",
"Location": "X3 Y3 X4 Y4",
"RoadName": "ABC ROAD",
"SpeedBand": 2,
"id": 214343
},
{
"DateTime": "2017-09-13T10:27:51.307349",
"LinkID": "109002906",
"Location": "X1 Y1 X2 Y2",
"RoadName": "ABC ROAD",
"SpeedBand": 2,
"id": 269214
},
{
"DateTime": "2017-09-13T10:42:36.724985",
"LinkID": "109002906",
"Location": "X1 Y1 X2 Y2",
"RoadName": "ABC ROAD",
"SpeedBand": 2,
"id": 327994
},
{
"DateTime": "2017-09-13T10:42:36.724985",
"LinkID": "109002907",
"Location": "X3 Y3 X4 Y4",
"RoadName": "ABC ROAD",
"SpeedBand": 2,
"id": 331903
},
{
"DateTime": "2017-09-13T10:42:36.724985",
"LinkID": "109002906",
"Location": "X1 Y1 X2 Y2",
"RoadName": "ABC ROAD",
"SpeedBand": 1,
"id": 349875
},
{
"DateTime": "2017-09-13T10:42:36.724985",
"LinkID": "109002907",
"Location": "X3 Y3 X4 Y4",
"RoadName": "ABC ROAD",
"SpeedBand": 2,
"id": 349876
},
. . .
],
"page": 1,
"total_pages": 1
}
答案 0 :(得分:0)
对于group by,您需要以下列格式指定feild。 通过...分组 表单对象列表:
{"field": <fieldname>}
此处fieldname是group by使用的列。