Rollup

Rollup fields are used to aggregate data from fields in the related table. Often used to calculate totals, averages, and other aggregate data.

Create a Rollup Field

Click on + icon to the right of Fields header
On the dropdown modal, enter the field name (Optional).
Select the field type as Rollup from the dropdown.
Select the link field from the dropdown. This is the field that links the current table to the related table.
Select the field for display from the dropdown. This is the field that will be displayed in the current table.
Select the aggregation function from the dropdown. This is the function that will be used to aggregate the data.
Click on Save Field button.

Here's a table with brief descriptions for each of the aggregation functions supported by NocoDB:

Aggregation Function	Description
Count	Counts the number of records in a dataset.
Minimum	Retrieves the minimum value from a dataset.
Maximum	Retrieves the maximum value from a dataset.
Average	Calculates the average value in a dataset.
Sum	Adds up all the values in a dataset.
Count Distinct	Counts the number of distinct values in a dataset.
Sum Distinct	Adds up all the distinct values in a dataset.
Average Distinct	Calculates the average of distinct values in a dataset.