I am new to knime and want to understand how the joiner node works.
I have left table with 16k records and I want to get a column from the right table.
The joiner node doubles the records and I get 32k records in my result.
Can someone please help me.
welcome to the forum.
You have to join all relevant key columns and the right table must be unique based on the defined key columns otherwise you get a m:n join.
Did you consider taking the free course to begin your journey in Knime ? It’s totally free, you have multiple lesson & level. And it shows you how the “aggregations” works in Knime (Join & Concatenate) : Self-Paced Courses List | KNIME
That being said, have you any experience in joining things (out of Knime) ?:
If you don’t want to take the course, you can refer to the two videos on YouTube explaining the joiner node (official Knime channel) ?:
ETL with KNIME. The Joiner Node - Part I - YouTube
ETL with KNIME. The Joiner Node - Part II - YouTube
Notice that if in your first table you have a key “A” that occurs twice in the second table, it will occurs twice in the joined table as well. That’s probably why you have 32k records.
For example, I want to join my customer table and my orders table on the customer id. If customer #1 (in the first table) has 3 orders (in the second table). The join will give you 3 lines in the joined table (each lines with the same customer & the different orders).
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