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Hello all, I'm bending my head over something that might have an obvious solution Im missing.
I have a big database in mssql and i'm using Grafana.
For retrieving a big piece of history I'd like to dynamically limit the returned results in my query.

What I have tried:

I have a log every second so I can get the total amount of rows by:

SET @TotalRows = DATEDIFF (SECOND, $__timeFrom(), $__timeTo())

Now I want to take every nth row to get a series of rough data.
the nth row is a percentage of the @TotalRows. Im my case I would like to calculate 1000000 (the max amount of rows) / @TotalRows

My query now looks like this

SELECT DateTime as time,
Value1 as "Value1",
Value2 as "Value2",
Value3 as "Value3"
WHERE DateTime > $__timeFrom() AND  DateTime < $__timeTo() 

I was looking into different approaches, but I can't really find a fitting one yet

Use dymamic sql queries - examples here Execute Dynamic SQL commands in SQL Server[^] or here - SQL Server Dynamic SQL[^]

Edit: Apologies for not reading your question properly
I want to take every nth row to get a series of rough data.
You can do something like this
	ROW_NUMBER() OVER (ORDER BY [DateTime]) as rn,
	Value1, Value2, Value3
	WHERE DateTime > $__timeFrom() AND  DateTime < $__timeTo()
SELECT *	-- I'm being lazy here
WHERE (rn % @n) = 0
order by rn;
Where @n is your "nth" calculation.

Incidentally using Value1 as "Value1", is pointless, just using Value1, will give exactly the same result. Also note the use of [ ] around the reserved word DateTime when it is used as a column name
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kenny_-_ 29-Dec-23 10:46am    
Now that is a great solution! I'm still learning in the SQL part, right now I have a solution that calculates the seconds an displays only the first couple of seconds of every minute. That was far from pretty, I like what you did I will test this soon. But I see that that will be a proper solution, thanks! And I know that "value1 as" is pointless, but it makes sense in the actual application, I just can't really post it as it is all closed source company stuff sadly.
Here is a comprehensive guide with multiple options for SQL Query with a Dynamic LIMIT:[^]
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CHill60 29-Dec-23 9:56am    
That link refers to LIMIT which is MySQL not MSSQL. Nor does it answer the OPs query - I made the same mistake initially, see my amended solution
M Imran Ansari 29-Dec-23 11:55am    
Oops! Thank you for the clarification.

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