Knime Joiner Node

[sri92]

Hello,
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.

[morpheus]

Hi @sri92,

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.

BR

[SamirAbida]

Hello @sri92,

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).

Br,
Samir