Central tendency

There are three descriptive measures of central tendency—the mean, the median, and the mode, but SQL Server does not have a way to calculate anything other than the mean directly. The arithmetic mean, or simply the mean (there are more types of mean in the central tendency), is the sum of all measurements divided by the number of observations in the dataset. The median is the middle value that separates the higher half from the lower half of the dataset. The median and the mode are the only measures of the central tendency that can be used for ordinal data, in which values are ranked relative to one another but are not measured absolutely. The mode is the most frequent value in the dataset. This is the only central tendency measure that can be used with nominal data, which has purely qualitative category assignments. For looking into such values with SQL Server, we will either need to define our own assembly with a custom aggregate or use complex T-SQL constructs to bypass the missing statistical functions. Another option would be to use the Python code or the R code; the code can be running inside the SQL Server, and you can pass the result set as the argument to the Python code or the R code to work on the descriptive statistics.