Match Unique vs Duplicate Dates

[tiger_78]

Hi, I need a solution to this...
I am comparing Sheet 1 Unique Dates, with Sheet 2 Duplicate Dates - both for the same Client.

My aim is to test with a 'True' or 'False' flag 'field I want', if a date matches or not - for each Client:

If any Date within a Client matches, Flag with TRUE
(the remaining Dates for that Client just leave Blank)

If any Date within a Client does not match, Flag with FALSE
Thanks!

Sheet 1

Unique Client No.	Operation Date
246777	20/07/2020
247051	21/07/2020
247099	25/07/2020
247174	01/07/2020
249650	14/08/2020

Sheet 2

Duplicate Client No.	Operation Date	field I want
246777	20/07/2020	TRUE
247051	21/06/2020
247051	21/07/2020	TRUE
247099	25/07/2020	TRUE
247174	01/05/2020
247174	01/06/2020
247174	01/07/2020	TRUE
249650	15/05/2020	FALSE
249650	15/06/2020	FALSE
249650	10/06/2020	FALSE

 

[tiger_78]

Hi thanks for your suggestions.
As no Date matches for 249650, I was expecting for this record to have one FALSE, such as below.

249650​	15/05/2020​
249650​	15/06/2020​	FALSE​
249650​	10/06/2020​