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以获取诸如此类的结果？

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

在MongoDB上，我会使用此类查询

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

尝试了多种方案，包括联接等

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

或

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

我尝试使用[0]或[]而不是[$]，但没有用

有人知道我如何以简单的方式解决此问题？

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

通过执行以下查询：选择food.id，servings.description 食物中的食物加入食物

您至少会得到以下结果：

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

不是您所期望的100％，但是也许您可以使用！

从CosmosDB中文档嵌套数组中的对象中选择值

2 个答案: