DocumentDB - 如何在查詢的SELECT部分​​返回距離？

Question

我想返回搜索座標和我正在搜索的字段之間的距離。

舉個例子，你可以使用這個 「查詢遊樂場」： https://www.documentdb.com/sql/demo#geospatial

他們使用下面的示例查詢：

-- Find all volcanoes of type Stratovolcano 
-- (http://www.sciencedaily.com/terms/stratovolcano.htm) 
-- that are within 100 km of Redmond, WA. 
SELECT * 
FROM volcanoes v 
WHERE ST_DISTANCE(v.Location, { 
    "type": "Point", 
    "coordinates": [-122.19, 47.36] 
    }) < 100 * 1000 
AND v.Type = "Stratovolcano" 
AND v["Last Known Eruption"] = "Last known eruption from 1800-1899, inclusive" 

，他們得到的結果如下：

{ 
    "Volcano Name": "Rainier", 
    "Country": "United States", 
    "Region": "US-Washington", 
    "Location": { 
    "type": "Point", 
    "coordinates": [ 
     -121.758, 
     46.87 
    ] 
    }, 
    "Elevation": 4392, 
    "Type": "Stratovolcano", 
    "Status": "Dendrochronology", 
    "Last Known Eruption": "Last known eruption from 1800-1899, inclusive", 
    "id": "33eff74b-e331-bca5-bf32-f8ece733465a", 
    "_rid": "FX8tANMM6QEeBAAAAAAAAA==", 
    "_ts": 1438994836, 
    "_self": "dbs/FX8tAA==/colls/FX8tANMM6QE=/docs/FX8tANMM6QEeBAAAAAAAAA==/", 
    "_etag": "\"00008304-0000-0000-0000-55c551940000\"", 
    "_attachments": "attachments/" 
} 

假設我想將火山（在[-121.758, 46.87]）和搜索座標之間的距離以米爲單位[-122.19, 47.36]

在我的T-SQL開發人員說，我可以把整個ST_DISTANCE位來自WHERE條款，幷包括其與SELECT這樣一起：

-- Find all volcanoes of type Stratovolcano 
-- (http://www.sciencedaily.com/terms/stratovolcano.htm) 
-- that are within 100 km of Redmond, WA. 
SELECT *, ST_DISTANCE(v.Location, { 
    "type": "Point", 
    "coordinates": [-122.19, 47.36] 
    }) 
FROM volcanoes v 
WHERE ST_DISTANCE(v.Location, { 
    "type": "Point", 
    "coordinates": [-122.19, 47.36] 
    }) < 100 * 1000 
AND v.Type = "Stratovolcano" 
AND v["Last Known Eruption"] = "Last known eruption from 1800-1899, inclusive" 

但是不起作用，它只是給我一個語法錯誤：

{ 
    "errors": [ 
    { 
     "severity": "Error", 
     "location": { 
     "start": 153, 
     "end": 154 
     }, 
     "code": "SC1001", 
     "message": "Syntax error, incorrect syntax near ','." 
    } 
    ] 
} 

我已經嘗試過許多東西，比如v.*，走樣的ST_DISTANCE結果與AS，但我不在任何地方，我都沒有找到我需要的谷歌。

那麼我需要做什麼？對於我來說，在一定距離內查詢是至關重要的，但如果我不得不重新計算客戶端的所有距離，那麼它的使用是有限的。

Answer 1

查詢必須使用SELECT v, ST_DISTANCE(...)代替SELECT *, ST_DISTANCE(...)。與ANSI-SQL類似，DocumentDB中的SELECT子句可以包含值列表或使用*，但不能同時使用兩者。

全面查詢：

-- Find all volcanoes of type Stratovolcano 
-- (http://www.sciencedaily.com/terms/stratovolcano.htm) 
-- that are within 100 km of Redmond, WA. 
SELECT v, ST_DISTANCE(v.Location, { 
    "type": "Point", 
    "coordinates": [-122.19, 47.36] 
    }) AS DistanceMetres 
FROM volcanoes v 
WHERE ST_DISTANCE(v.Location, { 
    "type": "Point", 
    "coordinates": [-122.19, 47.36] 
    }) < 100 * 1000 
AND v.Type = "Stratovolcano" 
AND v["Last Known Eruption"] = "Last known eruption from 1800-1899, inclusive"