The 'N' is a qualifier signifying a UNICODE string. Thus, the expression:
indicates that the string enclosed in quotes should be encoded as a UNICODE string, rather than the default encoding on the server it is running on. This guarantees that the string and the '@' especially, will be correctly interpreted even if the code is run on a server configured in Sanskrit, for example.
Not necessary if you're running the Latin character sets, but documentation writers can't guarantee that...
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