Get Started with MongoDB
Perform simple operations on resultset using Mongosh Cursor
In this lesson, we learn that the Mongosh Cursor is a data structure used by MongoDB to execute queries and manage result sets.
We cover how to sort results using the sort() method, specifying ascending or descending order based on properties like salary.
Additionally, we demonstrate how to limit the number of documents returned with the limit() method and count the size of the result set using count().
We also explore nested sorting by multiple properties, such as salary and age, to refine our query results further.
[00:00] Here we've got a query over the employees collection where we want to search for documents which have the skills array in which there would be at least one of the elements matching javascript or sql and just to make it easier for us to read the results, we just want to use the name in the resulting set, just except for the id property. So what we should realize that what Mongo is doing under the hood, it's actually a cursor, a specific Mongo shell data structure that is going to perform the query using a promise, query the Mongo for the content, whatever that is. And finally, when the cursor is being asked for giving the results, it's just going to display them over here. But essentially this is an object that allows us to perform more operations than what we thought initially. Now there is quite a lot of these such as forEach that we know from arrays such as Map, Limit and many other ones.
[01:02] So what we're going to use right now is to sort the collection. So sorting would look quite similar to what we've seen. So it's going to relate to the existing properties. So let's just sort by the salary. One, a positive value is going to be ascending.
[01:21] So let's just also include the salary into the result set. So that would be easier for us to compare the results. So, yep, this is in ascending order. In order to make a descending order obviously that would be the minus one value. Now another useful feature that we can use on the cursor data structure is we can limit the result set.
[01:46] So right now we've got the result set of length 5 and we can trim it down to 3 values. Finally, we don't need to use the count documents in order to count the result set, we can also use the count method. So without doing the limit one we have all of these now if we just added the limit one that would be reflected as well. Finally going back to sorting we could also provide a nested sort. So we might want to sort by the salary descending and finally by age ascending.
[02:28] Now this might not be reflected in the results since there might not be enough documents which would have the same salary, still that would be the way to go.