Question

Consider a student table with 104 rows in it. I need to create groups with a minimum of 10 students in each groups. In the case with 104 students, I would end up having 10 groups of 10 students and 1 group of 4 students if I iterate on each students and create the grouping. There’s a rule that a group with remaining students cannot have less than 5 students in it (in this case the last group consist of 4 student). Two possible approach I’m trying to do:

1. Roll up the last group that has less than 5 students and assign each of them to any groups, or
2. Spread the last group evenly to any groups.

How do I achieve any of these? Many thanks.

Eric

Answer 1

You can use ntile.

Distributes the rows in an ordered partition into a specified number
of groups. The groups are numbered, starting at one. For each row,
NTILE returns the number of the group to which the row belongs.

Some sample code:

declare @NumberOfStudents int
declare @StudentsPerGroup int

set @StudentsPerGroup = 10
set @NumberOfStudents = 104

select StudentID,
       ntile(@NumberOfStudents / @StudentsPerGroup) over(order by StudentID) as GroupID
from Students

Try it out on SE-Data.