Counts the number of unique values within a column or group.
field (required) The column of values to be counted. Duplicate and Null values are skipped.
- Finds the number of unique city names
More About Aggregate Functions
If the column being aggregated is grouped, then the aggregate is computed for each group. For example, if the worksheet is grouped by the column [Year], then placing Sum([Revenue]) on the [Year] level computes the revenue for each year.
The results of aggregate functions can be referenced by lower levels. An example would be to create a Sum([Amount]) column as Total and then an [Amount] / [Total] column as Percentage. This converts each Amount value into a relative percentage value.