Understanding $implicit
Let’s first understand how $implicit works. Suppose you’re asked to fetch data for individuals aged more than 18 and less than 30. How would you do that? Let’s explore through an example:
Imagine we have a database named school with a collection called students.
db.students indicates that we are working with the students collection.
The find method is used to search for all the matching data.
{ age: { $gte: 18, $lte: 30 } } is the search criteria, which specifies that we are looking for documents where the age is greater than or equal to 18 and less than or equal to 30.
Using $in
Now, suppose you are asked to fetch data for individuals aged 18, 20, 10, and 4. You can easily achieve this using $in. Let’s understand through an example:
db.students indicates that we are working with the students collection.
The find method is used to search for all the matching data.
{ age: { $in: [18, 20, 10, 4] } } is the search criteria, specifying that we are looking for documents where the age matches any of the values in the array [18, 20, 10, 4].
{ age: 1 } specifies that only the age property will be shown in the results.
Using $nin
$nin is the opposite of $in. In this case, you will get all data except for the values you provide. For example:
{ age: { $nin: [18, 20, 10, 4] } } is the search criteria, specifying that we are looking for documents where the age does not match any of the values in the array [18, 20, 10, 4].
{ age: 1 } specifies that only the age property will be shown in the results.
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