i am using MS SQL as tag historian with ignition. I am trying to query the SQL database using external software. I can see the explanation of table format and structure provided here.
Ignition Database Table Reference - Ignition User Manual 8.1 - Ignition Documentation (inductiveautomation.com)
But, i am wondering if anyone can share example queries that can simply read one tag over time range.
While this is technically possible, I’d recommend against it if you can help it. The reason being that your data is likely to be split across a variable number of tables. Assuming you know which tables you’re looking for ahead of time (based on the documentation you cited), I’d probably do something like this:
Given you know the table(s) you’re pulling from (and the tag datatype), it’s not terribly complex.
CREATE FUNCTION GetSingleIntTagHistory
SELECT t_stamp, intvalue
JOIN sqlth_te ON sqlth_te.id = sqlt_data_1_2022_05.tagid
WHERE tagpath = @tagPath
AND t_stamp BETWEEN @start AND @end
I wouldn’t know how to do it without knowing the table names ahead of time, but I think it’s possible.