DocumentDB SQL - Overview
DocumentDB is Microsoft's newest NoSQL document database platform that runs on Azure. In this tutorial, we will learn all about querying documents using the special version of SQL supported by DocumentDB.
NoSQL Document Database
DocumentDB is Microsoft's newest NoSQL document database, however, when we say NoSQL document database, what precisely do we mean by NoSQL, and document database?
SQL means Structured Query Language which is a traditional query language of relational databases. SQL is often equated with relational databases.
It is really more helpful to think of a NoSQL database as a non-relational database, so NoSQL really means non-relational.
There are different types of NoSQL databases which include key value stores such as −
- Azure Table Storage
- Column-based stores, like Cassandra
- Graph databases, like NEO4
- Document databases, like MongoDB and Azure DocumentDB
Why SQL Syntax?
SQL is just a language, but it's also a very popular language that's rich and expressive. Thus, it definitely seems like a good idea to use some dialect of SQL rather than come up with a whole new way of expressing queries that we would need to learn if you wanted to get documents out of your database.
How does SQL Work?
The DocumentDB team has answered this question in several innovative ways. Few of them are listed as follows −
First, assuming you've not changed the default behavior to automatically index every property in a document, you can use dotted notation in your queries to navigate a path to any property no matter how deeply nested it may be within the document.
You can also perform an intra-document join in which nested array elements are joined with their parent element within a document in a manner very similar to the way a join is performed between two tables in the relational world.
Your queries can return documents from the database as it is, or you can project any custom JSON shape you want based on as much or as little of the document data that you want.
SQL in DocumentDB supports many of the common operators including −
Arithmetic and bitwise operations
AND and OR logic
Equality and range comparisons
The query language also supports a host of built-in functions.