azure-cosmosdb - 从 CosmosDB 中文档嵌套数组中的对象中选择值

Question

想象一下我们有一个这样的集合(示例取自 https://www.documentdb.com/sql/demo )

{
    "_id" : "19015",
    "description" : "Snacks, granola bars, hard, plain",
    "servings" : [ 
        {
            "amount" : 1,
            "description" : "bar",
            "weightInGrams" : 21
        }, 
        {
            "amount" : 1,
            "description" : "bar (1 oz)",
            "weightInGrams" : 28
        }, 
        {
            "amount" : 1,
            "description" : "bar",
            "weightInGrams" : 25
        }
    ]
}

我如何在 SQL api 中查询 CosmosDB 以获得这样的结果？

{
    "_id" : "19015",
    "servings" : [ 
        {
            "description" : "bar"
        }, 
        {
            "description" : "bar (1 oz)"
        }, 
        {
            "description" : "bar"
        }
    ]
}

在 MongoDB 我会使用这样的查询

db.getCollection('food').find({id: '19015'}, {'servings.description' : 1})

用连接等尝试了多个场景

SELECT 
    food.id,
    food.servings.description
FROM food
WHERE food.id = "19015"

或者

SELECT 
    food.id,
    [{
        description: food.servings[0].description
    }] AS servings
FROM food
WHERE food.id = "19015"

而不是 [0]我试过 []或 [$]但不起作用

有人知道我如何以简单的方式解决这个问题吗？

Answer 1

您可以使用 ARRAY(subquery) 表达式来实现这一点。这是查询:

SELECT
    food.id,
    ARRAY(SELECT serving.description FROM serving IN food.servings) AS servings
FROM food
WHERE food.id = "19015"