Hitachi Vantara Pentaho Community Wiki
Skip to end of metadata
Go to start of metadata

Description

The Database Join step allows you to run a query against a database using data obtained from previous steps. The parameters for this query are specified as follows:

  • The data grid in the step properties dialog.  This allows you to select the data coming in from the source hop.
  • As question marks (?) in the SQL query.  When the step runs, these will be replaced with data coming in from the fields defined from the data grid.  The question marks will be replaced in the same order as defined in the data grid. 

For example, Database Join allows you to run queries looking up the oldest person who bought a specific product as shown below:

SELECT      customernr
FROM        product_orders, customer
WHERE       orders.customernr = customer.customernr
AND         orders.productnr = ?
ORDER BY    customer.date_of_birth

The grid is then defined as follows:

When the step runs, the (?) placeholder defined in the SQL query will be replaced with the incoming productnr field value from the source hop.  To define and use multiple parameters, list the fields in order you want them to be replaced in the SQL statement.

Options

The following table desribes the options for the Database Join step:

Option

Description

Step name

Name of the step; This name has to be unique in a single transformation

Connection

The database connection to use for the query.

SQL

SQL query to form the join; use question marks as parameter placeholders

Number of rows to return

Zero (0) returns all rows; any other number limits the number of rows returned.

Outer join?

Enable to always return a result, even if the query did not return a result

Parameters table

Specify the fields containing parameters.  The parameter type is required.

  • No labels