    { measure_column [ { condition | expr }[ , { condition | expr } ...] ]
    | aggregate_function
            { [ { condition | expr }[ , { condition | expr } ...] ]
            | [ single_column_for_loop [, single_column_for_loop] ... ]
            | [ multi_column_for_loop ]
            }
    | analytic_function
    }
    Note: The outside square brackets shown in bold are part of the syntax.
          In this case, they do not represent optionality.