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.

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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.

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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.

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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.

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