How do you configure the Joiner node in KNIME to perform a left outer join that retains all customers even if they have no transactions?

Configure the Joiner node by connecting the Customer Master Data to the upper input (left table) and the Transaction History to the lower input (right table). In the Matching Criteria section, select CustomerID as the key for both tables. Under Include in Output, tick only Matching rows and Left unmatched rows, and leave Right unmatched rows unchecked. This retains all customers, including those with no transactions.

In KNIME, the Joiner node combines two tables based on a shared key. To keep all customers even when they have no matching transactions, you perform a left outer join. First, add the Joiner node to the workflow and connect the output of the CSV Reader (Customer Master Data) to the top input port, which represents the left table. Connect the Excel Reader output (Transaction History) to the bottom input port for the right table. Open the Joiner configuration and, in the Matching Criteria section, choose CustomerID as the matching column for both the top input and the bottom input. In the Include in Output options, tick Matching rows, which includes customers who have purchases, and Left unmatched rows, which includes customers without any transactions. Leave Right unmatched rows unchecked so that transactions without a matching customer profile are not included. After applying and executing, the joined output will show every customer with their transaction details, and customers without transactions will have missing values in the transaction columns.