In MongoDB, the $sum aggregation pipeline operator calculates and returns the sum of numeric values.
MongoDB
MongoDB $avg Aggregation Pipeline Operator
In MongoDB, the $avg aggregation pipeline operator calculates and returns the average value of the specified numeric values.
MongoDB $substrBytes
In MongoDB, the $substrBytes aggregation pipeline operator returns the substring of a string, based on the specified UTF-8 encoded bytes indexes.
MongoDB $substrCP
In MongoDB, the $substrCP aggregation pipeline operator returns the substring of a string, based on the specified UTF-8 code point indexes.
MongoDB $strLenCP
MongoDB, the $strLenCP aggregation pipeline operator returns the number of UTF-8 code points in the specified string.
The $strLenCP operator is different to the $strLenBytes operator, which returns the number of bytes in the string.
MongoDB $strLenBytes
MongoDB, the $strLenBytes aggregation pipeline operator returns the number of UTF-8 encoded bytes in the specified string.
Each character in a string can contain contain a different number of bytes, depending on the character being used. The $strLenBytes operator can figure out how many bytes each character contains and return the correct result for the whole string.
MongoDB $stdDevPop
In MongoDB, the $stdDevPop aggregation pipeline operator calculates the population standard deviation of its input values.
The input values can be from a group of documents (i.e. documents that are grouped by the same key), or they can be multiple fields within a single document.
MongoDB $stdDevSamp
In MongoDB, the $stdDevSamp aggregation pipeline operator calculates the sample standard deviation of the input values.
The input values can be from a group of documents (i.e. documents that are grouped by the same key), or they can be multiple fields within a single document.
MongoDB $strcasecmp
In MongoDB, the $strcasecmp aggregation pipeline operator performs a case-insensitive comparison of two strings.
It returns either 1, 0, or -1, depending on whether or not the first string is greater than, equal to, or less than the second string.
How to Delete MongoDB Documents by Importing a File
As of mongoimport version 100.0.0, you can delete documents in MongoDB based on an imported file. To do this, use delete mode.
When you use delete mode, if an imported document has the same _id value as an existing one in the collection that you’re importing into, the existing document will be deleted.
You can also specify another field or fields (other than the _id field) to be the matching field if required.