Z-Score in SQL based on last 1 year - sql

Question

I have daily data structured in the below format. Please note this is just a subset of the data and I had to make some modifications to be able to share it.
The first column is the [DataValue] for which I need to find the Z-score by IndexValue, [Qualifier], [QualifierCode] and [QualifierType]. I also have the [Date] column in there.
I essentially need to find the Z-score value for each data point by IndexValue, [Qualifier], [QualifierCode] and [QualifierType]. The main point of focus here is that I have data for the last 3 years but in order to calculate Z-score, I only want to take the average and standard deviation for the last one year.
Z-Score = [DataValue] - (Avg in last 1 year) / (Std Dev in last 1 year)
I am struggling with how to get average for the last one year. Would anybody be able to help me with this?
SELECT [IndexValue]
,[Qualifier]
,[QualifierCode]
,[QualifierType],[Date]
,[Month]
,[Year]
,[Z-Score] = ([DataValue] - ROUND(AVG([DataValue]),3))/ ROUND(STDEV([DataValue]),3)
FROM [TABLEA]
GROUP BY [IndexValue]
,[Qualifier]
,[QualifierCode]
,[QualifierType]
,[Date]
,[Month]
,[Year]
order by [IndexValue]
,[Qualifier]
,[QualifierCode]
,[QualifierType]
,[Date] desc
: https://i.stack.imgur.com/pqhJD.png

Answer 1

You need window functions for this:
SELECT a.*,
( (DataValue - AVG(DataValue) OVER ()) /
STDEV(DataValue) OVER ()
) as z_score
FROM [TABLEA] a;
Note: if data_value is an integer, you will need to convert it to a number with digits:
SELECT a.*,
( (DataValue - AVG(DataValue * 1.0) OVER ()) /
STDEV(DataValue) OVER ()
) as z_score
FROM [TABLEA] a;
Rounding for the calculation seems to be way off base, unless your intention is to produce a z-like score that isn't really a z-score.