In the below query, we have a table named Person containing EnrollmentDate and so on. This Enrollment column allows nulls while insertion. We are performing the select command based on EnrollmentDate column which is not null. ie, first it checks only for the rows that contain a value in the Enrollment column, then performs GroupBy.
Then it searches for the rows that contains the same EnrollmentDate, counts the number of rows and displays them in the StudentCount column.
Suppose if we have a table like below:
Then the ouput will be
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