In MongoDB, the $slice aggregation pipeline operator returns a subset of an array.
To use $slice, you specify the number of elements to return from the array. You can also specify a starting position for which to take the subset from the array.
2 Ways to Limit the Documents Returned in MongoDB
When you run queries In MongoDB, you have the option of limiting the documents returned. This is where you specify a maximum number of documents to be returned by the operation.
For example, if an operation would normally return 2,000 documents, but you specify a limit of 1,000, then only 1,000 documents are returned. However, if the operation would only return say, 500 documents, then all 500 are returned (because they don’t breach the 1,000 document limit).
This is a bit like using the TOP clause in SQL Server, or the LIMIT clause in MySQL, MariaDB, PostgreSQL, and SQLite.
How to fix “Server is not configured for RPC” Msg 7411 using T-SQL
If you’ve encountered error Msg 7411, Level 16 in SQL Server, it’s because you need to enable “RPC out” on the linked server that you’re trying to execute code on.
Continue readingMongoDB $size
In MongoDB, the $size aggregation pipeline operator counts and returns the total number of items in an array.
The $size operator accepts one argument. The argument can be any valid expression that resolves to an array.
4 Ways to Delete a Document in MongoDB
In MongoDB, if you need to delete a document in the mongo shell, you can use:
- The
db.collection.remove()method - The
deletecommand - The
db.collection.deleteOne()method - The
db.collection.deleteMany()method
This article provides examples of each.
Continue readingMongoDB $setUnion
In MongoDB, the $setUnion aggregation pipeline operator accepts two or more arrays and returns an array containing the elements that appear in any of those input arrays.
$setUnion accepts two or more arguments, all of which can be any valid expression as long as they each resolve to an array. $setUnion treats the arrays as sets.
MongoDB $setIsSubset
In MongoDB, the $setIsSubset aggregation pipeline operator accepts two arrays and returns true when the first array is a subset of the second, and false when it isn’t.
The first array is also considered a subset when it equals the second array.
Continue readingMongoDB $setIntersection
In MongoDB, the $setIntersection aggregation pipeline operator accepts two or more arrays and returns an array that contains the elements that appear in all input arrays.
$setIntersection accepts two or more arguments, all of which can be any valid expression as long as they each resolve to an array. $setIntersection treats the arrays as sets.
MongoDB $setEquals
In MongoDB, the $setEquals aggregation pipeline operator compares two or more arrays and returns true if they have the same distinct elements and false otherwise.
$setEquals accepts two or more arguments, all of which can be any valid expression as long as they each resolve to an array. $setEquals treats the arrays as sets.
MongoDB $setDifference
In MongoDB, the $setDifference aggregation pipeline operator accepts two sets and performs a relative complement of the second set relative to the first. It returns an array containing the elements that only exist in the first set.
$setDifference accepts two arguments, both of which can be any valid expression as long as they each resolve to an array. $setDifference treats the arrays as sets.