从CosmosDB中文档嵌套数组中的对象中选择值

Question

想象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以获取这样的结果？

{
    "_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})

使用联接等尝试了多个方案

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

要么

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

• 而不是[0]我尝试过[]，[$]但不起作用

有人知道我如何以简单的方式解决此问题吗？

Answer 1

您可以使用ARRAY（subquery）表达式来实现此目的。这是查询：

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

Answer 2

通过执行此查询：

select food.id, servings.description
from food join servings in food.servings

你至少会得到以下结果：

{"id":19015, "description":"bar"}
{"id":19015, "description":"bar (1 oz)"}
{"id":19015, "description":"bar"}

不是 100% 符合您的预期，但也许是您可以使用的东西！