Merging tables by date range in PowerBI - merge

Question

I have 2 tables:
Table 1: enrollment
student_id enrollment_date
1000 4/26/2022
1001 11/15/2022
1002 6/6/2022
1003 9/6/2022
1001 9/14/2022
1004 9/21/2022
1002 11/13/2022
1005 12/27/2022
Table 2: promotion
promo_id promotion promo_start promo_end
1 30% Promo 9/5/2022 9/26/2022
2 Christmas Promotion 12/25/2022 12/31/2022
3 11.11 Promotion 11/11/2022 11/15/2022
What I want to achieve is to merge 2 tables together based on date range defined in promotion table. If the enrollment_date did not fall into any promotion period, then just leave it as null. Below is the expected output:
Any advise or help will be greatly appreciated!

Answer 1

Here you go.
let
Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("RYxBCoAgEEWvIgPtIv0jBq27QHtp0a4WJaj3J0lz/u495o33BFVHI1kzqC2GO6i+YhftNBvmn3j+kPbRE8vZesYr5ftI9UW+wlMsWHPLK1lIbaUGJkDKbjUgdSHX6v0F", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [promo_id = _t, promotion = _t, promo_start = _t, promo_end = _t]),
#"Changed Type" = Table.TransformColumnTypes(Source,{{"promo_id", Int64.Type}, {"promotion", type text}, {"promo_start", type text}, {"promo_end", type text}}),
#"Changed Type with Locale" = Table.TransformColumnTypes(#"Changed Type", {{"promo_end", type date},{"promo_start", type date}}, "en-US")
in
#"Changed Type with Locale"
let
Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("dc7LCcAwDAPQVYrPAVnKp2SW0P3XKA0lrQ/x9SHJYxjd/ZhnyQrUIJfsSpO4iARrMC1riKm8pGPX18ESqPxI3Cw9X+Rg9TNB52vXDQ==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [student_id = _t, enrollment_date = _t]),
#"Changed Type" = Table.TransformColumnTypes(Source,{{"student_id", Int64.Type}, {"enrollment_date", type text}}),
#"Changed Type with Locale" = Table.TransformColumnTypes(#"Changed Type", {{"enrollment_date", type date}}, "en-US"),
#"Added Custom" = Table.AddColumn(#"Changed Type with Locale", "promo_id", (x)=> Table.SelectRows(promotion, (y)=> x[enrollment_date] >= y[promo_start] and x[enrollment_date] <= y[promo_end]){0}?[promo_id]?)
in
#"Added Custom"