I started my learning journey with Tableau few months ago.
So far , it is pretty good. However , I found LOD ( level of detail) expressions are interestingly complex
at the first encounter. Reading thru few examples and watching few videos to get a better understanding of these concepts.
Being I come from database background and SQL knowledge , I am hoping , I can provide my understanding of LOD thru ranking/ analytical
functions.
Please see my blog posts on ranking / analytical functions here
https://mfzahirdba.blogspot.com/2009/10/analytics-20.html
https://mfzahirdba.blogspot.com/2009/11/analytics-20-part-ii.html
https://mfzahirdba.blogspot.com/2018/10/windowing-clause-why-it-matters.html
https://mfzahirdba.blogspot.com/2013/08/oracles-analytical-functions-vs-sql.html
https://mfzahirdba.blogspot.com/2012/09/difference-between-percentilecont-and.html
There are three LOD keywords ( FIXED , INCLUDE , EXCLUDE) in Tableau.
FIXED LOD calculations does not depend on the visuals ( aka viz) , where as visulation impacts
how INCLUDE and EXCLUDE are calculated.
In my example , I have created a table in SQL server and populated few records.
To follow along the example , feel free to use the script below.
Create table CourseEnrollment
( StudentName varchar(50) ,
Department varchar(50) ,
Subject varchar(50) ,
EnrollmentDate Date
) ;
GO
Insert into CourseEnrollment values ( 'Zahir Mohideen' , 'Maths' , 'Pre Calculus' , '1988-03-01') ;
Insert into CourseEnrollment values ( 'Zahir Mohideen' , 'Maths' , 'Multivariate Calculus' , '2010-05-16') ;
Insert into CourseEnrollment values ( 'Zahir Mohideen' , 'Statistics' , 'Statistics 101' , '2020-07-25') ;
Insert into CourseEnrollment values ( 'Abdul Hameed' , 'Maths' , 'Pre Calculus' , '1991-03-01') ;
Insert into CourseEnrollment values ( 'Abdul Hameed' , 'Physics' , 'Phy101' , '2020-07-25') ;
Let us bring in these LOD calculations into the sheet .
When we remove the department / Student , the FIXED LOD remains the same ; there is a change in Include and Exclude.
