Sql-server – How to store very small values (E-314) in SQL Server database

Technically to display n-th value you use the ranking functions like RANK, DENSE_RANK or ROW_NUMBER. Which one exactly depends, but what you describe matches best ROW_NUMBER:

with cte as (
 select row_number() over (order by Date) as rn, *
 from table)
where rn % 1000 = 0;

But you are saying that you want o do this for performance reasons, avoid going through millions of rows. Such a query had already done the damage, it read from disk all the rows and had to sort them so the performance price was already payed.

A better alternative to selecting a random sample of data is to use the TABLESAMPLE clause, see Limiting Result Sets by Using TABLESAMPLE:

select * 
from table tablesample (100 rows);

TABLESAMPLE will be way more efficient as it actually avoids reading all the data, it only samples some of the pages in the table and returns all rows in the sampled pages.

But consider that if you use TABLESAMPLE your WHERE clause are applied after the sampling. So it may be that the sample does not contain any row for the device/sensor you're interested in. This is specially true for sensor with small data.

An INSTEAD OF INSERT trigger performs actions instead of what the original INSERT would have done.

In your code, if either @appr_username or @appr_id is NULL, some sort of change is made to the base table (an insert or an update).

Otherwise, nothing is done by the trigger (no rows affected), so the AFTER triggers are skipped. After all, SQL Server thinks, if the INSTEAD OF trigger did nothing, there can't be anything for an AFTER trigger to do either, right?

Note you can also get some very confusing behaviours if the server configuration option nested triggers (shown as Allow Triggers to Fire Others in the SSMS Advanced Server Properties Tab) is set to 1 (the default).

From that link:

The nested triggers option controls whether an AFTER trigger can cascade. That is, perform an action that initiates another trigger, which initiates another trigger, and so on. When nested triggers is set to 0, AFTER triggers cannot cascade. When nested triggers is set to 1 (the default), AFTER triggers can cascade to as many as 32 levels. INSTEAD OF triggers can be nested regardless of the setting of this option.