Talend tMap to Row Number using Variables

Below is a short video which walks you through a different method to derive a row_number, within Talend Open Studio, using the variables within tMap.

https://youtu.be/UbPU7VVu-fU





The notes within the video are below:


20191101 Talend TOS Using tMap to calculate the row number, using the variables

FileInputDelimited > SortRow > tMap > LogRow

select
*
,row_number() over (partition by name order by exam_date) as rn
from name_grades


name,subject,grade,exam_date
andrew,maths,a,2019/01/01
andrew,english,b,2019/01/02
andrew,science,c,2019/01/03
boris,maths,c,2019/01/01
boris,english,a,2019/01/02
boris,science,g,2019/01/03
jeremy,maths,a,2019/01/01
jeremy,english,a,2019/01/02
jeremy,science,a,2019/01/03
donald,maths,u,2019/01/01
donald,english,u,2019/01/02
donald,science,u,2019/01/03


** var expressions **
name = input name
rn = Var.previous_name == null ? 1 : (    Var.name.equals(  Var.previous_name ) ?   Var.rn + 1 : 1  )
previous_name = input name