Joins

Pentaho Joins ..

There are different types of joins that you can use in Pentaho to combine data from different sources based on a common key or condition.

Here are some joins we are going to cover in this section:

Workshops

Cross

A Pentaho cross join is a way of combining two streams of data in a Cartesian product, meaning that every row from one stream is joined with every row from the other stream. This can be useful for creating combinations of values or performing calculations based on multiple inputs.

However, a cross join can also result in a very large output, especially if the input streams have many rows. Therefore, it is important to optimize the cross join step by using filters, conditions, or lookups to reduce the number of rows or columns in the output.

Cross Join

Merge

There are four basic types of SQL joins: inner, left, right, and full. The easiest and most intuitive way to explain the difference between these four types is by using a Venn diagram, which shows all possible logical relations between data sets. Again, it's important to stress that before you can begin using any join type, you'll need to extract the data and load it into an RDBMS, where you can query tables from multiple sources.

Joins

Merge Join

Database

The Database Join step allows you to run a query against a database using data obtained from previous steps or parameters.

Database Join