问题
I want to know if my value is included in an interval consisting of the previous row and the next row. How to do it in Talend?
I tried a tMemorizeRow function where I save 3 lines each time, but encountered a java.lang.NullPointerException exception as when I am on the first line it does not know the next row I saved.
What am I missing?
回答1:
You can try this : add a column "sequence" with value as Numeric.sequence("s1",1,1)to your data : this way you'll know this exact order between rows in your flow (you can do it in a tMap). Redirect the tMap to a tHashOutput component (if you can't find in the palette, add it through Project Parameters>Designer>Palette>Technique , this component is hidden by default).
Then you'll need an other subjob, with 3 tHashInput : one for your main flow, and the two others as lookup : then you'll be able to join rows with previous and following one , thanks to your 'sequence' field.
Then in tMap_2 you'll be able to compare values from mainFlow with Previous and Next flows.
来源：https://stackoverflow.com/questions/57996478/comparison-between-current-row-previous-row-and-next-row-in-talend