Implement queries that use array and type-checking functions

Queries play a crucial role in designing and implementing native applications using Microsoft Azure Cosmos DB. In this article, we will explore how to implement queries that use array and type-checking functions in Azure Cosmos DB.

Azure Cosmos DB offers a rich query language called SQL (Structured Query Language) API that allows you to perform complex queries on your data. Let’s dive into some commonly used array and type-checking functions that can enhance your query capabilities.

1. ARRAY_CONTAINS

The ARRAY_CONTAINS function is used to check if an array contains a specific element. This function takes two parameters: the array to check and the value to search for. It returns a Boolean value indicating whether the value is present in the array.

sql
SELECT c.name, c.category
FROM c
WHERE ARRAY_CONTAINS(c.tags, ‘Cosmos DB’)

In the above example, we retrieve documents where the ‘tags’ array contains the value ‘Cosmos DB’. This function is useful when dealing with arrays of values, such as tags or categories.

2. ARRAY_LENGTH

The ARRAY_LENGTH function allows you to determine the number of elements in an array. It takes a single parameter, which is the array to calculate the length of, and returns an integer specifying the array length.

sql
SELECT c.name, ARRAY_LENGTH(c.comments) AS commentCount
FROM c

In the above example, we retrieve documents along with the count of comments present in the ‘comments’ array. This function helps in performing aggregations or filtering based on array length.

3. IS_DEFINED

The IS_DEFINED function is used to check if a property exists or is defined within a document. It takes a single parameter, which is the property to check, and returns a Boolean value (true or false).

sql
SELECT c.name, c.price
FROM c
WHERE IS_DEFINED(c.price)

In the above example, we retrieve documents where the ‘price’ property is defined. This function assists in handling optional properties or performing conditional filtering.

4. IS_STRING

The IS_STRING function checks if a value or expression is of string type. It takes a single parameter and returns a Boolean value.

sql
SELECT c.name, c.value
FROM c
WHERE IS_STRING(c.value)

In the above example, we retrieve documents where the ‘value’ property is of string type. This function is helpful when working with multiple data types or grouping documents based on their data type.

By utilizing these array and type-checking functions, you can efficiently query and manipulate your data in Azure Cosmos DB. It’s recommended to refer to the Azure Cosmos DB documentation for a comprehensive list of available functions and their usage.

In conclusion, the ability to implement queries using array and type-checking functions is essential when designing and implementing native applications using Microsoft Azure Cosmos DB. These functions provide flexibility and efficiency in managing and querying data.