SQL-query help needed - sql

Question

I guess my first question was not really clear so here is it again.
I wrote a query that does not select the last five rows in my dataset:
with query AS
(select ROW_NUMBER() over (PARTITION BY SchemaName, TableName order by StartTime desc) AS num,
from logging.ImportLogging_MSH)
Select
from query
where num > 5 and SchemaName = 'opps' and TableName = 'vs4_status_history_address'
I want to extend my query so that it checks if any of the last five rows in EndTime has a NULL value, then the query skips that row, I do not however want to remove all null values in my Endtime.
My idea was to create an integer variable that gets incremented if EndTime has a null value
e.g. in java it'll usually be like this:
int x = 5;
if (EndTime == null) {
x++;
}
so I tried to add this to my query which is not correct:
declare #n INT = 5
with query AS
(select ROW_NUMBER() over (PARTITION BY SchemaName, TableName order by StartTime desc) AS num,
from logging.ImportLogging_MSH)
Select ,
case when EndTime is null then #n = #n + 1 end
from query
where num > n and SchemaName = 'opps' and TableName = 'vs4_status_history_address'
It's an assignment from my new student job and I don't want to ask around a lot on my first day so if you guys have any suggestions it'll help me a lot :)
both queries with and without the last 5 rows
The desired result I'm trying to get but this problem with this approach is that all NULL values in EndTime are removed, which I should that do
with query AS
(select ROW_NUMBER() over (PARTITION BY SchemaName, TableName order by StartTime desc) AS num, *
from logging.ImportLogging_MSH
where EndTime is not null)
Select *
from query
where num > 5 and SchemaName = 'opps' and TableName = 'vs4_status_history_address'
select *
from logging.ImportLogging_MSH
where SchemaName = 'opps' and TableName = 'vs4_status_history_address'
enter image description here
as you can see here, the last four rows that contain null values in EndTime are removed and the next last 5 rows are not selected
I'm trying to write this same query but without removing all null values off Endtime
The answer I'm getting when writing Steve's query
enter image description here