Overview
This processor executes a left join on two input Datasets by one matching column. Columns selected as join partners must have same data types. All other columns in the two Datasets may not have identical names, the left table is the leading table.
LEFT JOIN returns all records from the left table (table1), and the matched records from the right table (table2). The result is NULL from the right side, if there is no match.
Left join syntax
SELECT column_name(s)
FROM table1
LEFT JOIN table2
ON table1.column_name = table2.column_name;
Input
The processor requires two input Datasets having one attribute column in common. The join operation will be based on this common column. The left input port in the processor corresponds to the displayed Dataset.
Configuration


Output
The result contains columns from both the first and the second input Datasets. It will include all the entries from the first Dataset and the matching ones from the second.
Note that in case of a mismatch, a default value can be defined using the last configuration filed.
Example
In the following example we join two custom input tables using the left join processor.
Workflow


Input tables
First Table
OrderID | CustomerID | OrderDate |
10308 | 2 | 1996-09-18 |
10309 | 37 | 1996-09-19 |
10310 | 77 | 1996-09-20 |
Second Table
CustomerID | CustomerName | Country |
1 | Alfred | Germany |
2 | Ana Trujillo | Mexico |
3 | Antonio Moreno | Mexico |
Note here that not all the customer IDs in the second table are available in the first one.
Example Configuration
Result
As mentioned before, the left table was fully displayed, and corresponding entries from the right table were added.
The data in the added columns having no corresponding values in the second table is left empty.
Relevant Articles
Was this article helpful?
That’s Great!
Thank you for your feedback
Sorry! We couldn't be helpful
Thank you for your feedback
Feedback sent
We appreciate your effort and will try to fix the article