Exploring server-side programming

Azure Cosmos DB server-side programming consists of stored procedures, triggers, and user-defined functions (UDFs) written in JavaScript.

Implementing user-defined functions

UDFs can only be called from within a query, and they implement custom business logic like calculating tax.

Let’s define a UDF to calculate the sales tax of products:

1. In the Azure Cosmos DB Emulator or Azure portal Data Explorer, create a new UDF, as shown in Figure 4.9:

Figure 4.9: Creating a new UDF

2. For the User Defined Function Id, enter salesTax.
3. For the User Defined Function Body, enter JavaScript to define the salesTax function, as shown in the following code:

   function salesTax(unitPrice){
       return unitPrice * 0.2;
   }
   

4. In the toolbar, click Save.
5. Create a new SQL query and enter SQL text to return the unit price and sales tax for products that cost more than 100, as shown in the following...