Question

I am currently working on a project that is looking at having a database that will store only 2 rows of data in it. This database will have new rows added to it all the time and the top row will be deleted when a new row is entered making sure there are always 2 rows.

What I am looking to do is to compare the top row of data and the bottom row of data and then store the data that is different in variables. I only want to store the data that is different from the bottom row as the top row will always be the oldest sets of data and I would no longer need to handle that.

I can do this all on the C# side but I was wondering if there is a way to do most of this on the SQL side of things? Thanks for the help 🙂

Answer 1

thanks for the clearification, let assume this table:

create table temp_monitor(id int, stamp datetime, @newTemp1 float, @newTemp2 float)

then this stored procedure should do the trick

create proc updateTempMonitor(temp_oven_1 float, temp_oven_2 float)
as

-- save the values where about to replace
declare @id int, @t1 float, @t2 float
select top 1 @id = id, @t1 = temp_oven_1, @t2 = temp_oven_2 from temp_monitor order by stamp

-- update the oldest
update updateTempMonitor set temp_oven_1 = @newTemp1, temp_oven_2 = @newTemp2 where id = @id

-- return data to caller (c#)
select @t1, @t2