Conditional Operators
Now that you have learned how to query MongoDB collections, as well as how to use projection to return only specific fields in the output, it is time to learn more advanced ways of querying. So far, you've tried to query the comments collection using the value of a field. However, there are more ways to query documents. MongoDB provides conditional operators that can be used to represent various conditions, such as equality, and whether a value is less than or greater than some specified value. In this section, we will explore these operators and learn how to use them in queries.
Equals ($eq)
In the preceding section, you saw examples of equality checking where the queries used a key-value pair. However, queries can also use a dedicated operator ($eq) to find documents with fields that match a given value. For example, the following queries find and return movies that have exactly 5 comments. Both queries have the same effect:
db.movies.find({"...
