Calculating distinct counts
The COUNT() function has a variant which can be quite useful: COUNT(DISTINCT). This distinct count function allows us to calculate the number of unique elements in a data set, so COUNT(DISTINCT x.Y) will get the unique number of values for column Y on the table aliased as x.
In this example, you will continue to look at incident rollup data in the dbo.IncidentRollup table. Management would like to know how many unique incident types we have in our three-month data set as well as the number of days with incidents.
They already know the total number of incidents because you gave them that information in the last exercise.
This exercise is part of the course
Time Series Analysis in SQL Server
Exercise instructions
- Return the count of distinct values in
IncidentTypeIDasNumberOfIncidentTypes. - Return the count of distinct values in
IncidentDateasNumberOfDaysWithIncidents
Hands-on interactive exercise
Have a go at this exercise by completing this sample code.
-- Fill in the functions and columns
SELECT
___(___ ir.___) AS NumberOfIncidentTypes,
___(___ ir.___) AS NumberOfDaysWithIncidents
FROM dbo.IncidentRollup ir
WHERE
ir.IncidentDate BETWEEN '2019-08-01' AND '2019-10-31';