AS alias assigns a column title to a result. The word AS is optional.

This function overrides the title assigned to an element in the definition of its aggregate, as the title of the column of the results table. The alias name is limited to 16 characters; longer values are truncated and only the first 16 characters are used. The first character of the alias name must be alphabetic, and the remaining characters must be alphanumeric or @, #, $, or _.