Simple queries

As you can see from the preceding diagram, the query (also referred to as query criteria or filter) can be as simple as using JSON syntax to identify a document field, and the value it equals. As an example, we will use the customers collection in the sweetscomplete database. When you specify a query filter, you can provide a hardcoded value, as shown here:

db.customers.findOne({"phoneNumber":"[phone]"});

However, you can also simply wrap the target value into a regular expression by surrounding the target string with delimiters ("/"). Here is a simple example, whereby we use the db.collection.findOne() command to return a single customer record where the target phone number is located using a /44-118-652-0519/ regular expression:

Let's say that the management has asked you to produce a count of customers. In this case, you can use a cursor method to operate on the results. To form this query, simply execute db.collection...