SQL - Date Difference when the column header is the same!

[MaryCann]

Howdy you wonderful Alteryx community!  I am going to conquer SQL one day - may not be for 10-years, but, it will occur.  

Todays problem:  I am trying to figure out the number of days between the first Tx Plan Final Approval Date and the next Tx Plan Final Approval Date.  Notice, it's the same Column Header!  So, I thought Rank - count the number of Tx Plan Final Approval Dates per case number.  But, now I'm stuck...  Here's a snip:

Ike that 7/13/2021 and the 7/15/2021 - 2 days, the next step will be to filter out everything less than 30 days.  But, how do I write the SQL for this?

A Pre-Thank You to all you awesome folks for responding!

[MaryCann · Accepted solution]

Ignore everybody!  I figured it out!  Multi - Row Formula Tool to the rescue.  😁