What I want to is to delete Row 2 which is the same as in Row 1. When you look at the ComplaintNumber you will notice there is a duplicate of Complaint. But when i try to delete the duplicate it complaints about the child table which is in CASE table. Even there I can delete because even the Child Table has a relationship with other tables in the same Database.
It would help if you started by explaining what you mean by "duplicate cases" and also what it means to delete those cases.
My guess is that you don't actually want to delete anything from the database, you just want a different query which shows fewer rows.
I'm also guessing that, for example, you consider Rows 1 and 2 of the output of the working query to be "duplicate cases" because they both have the same case number. However I'm unable to guess whether you just want to show one of them (and if so, which one) or whether you don't want to show either of them.
But guessing isn't that useful. So go ahead and clarify your question.