FILTER TRANSFORMATION

                                                      

• Active and connected transformation.

We can filter rows in a mapping with the Filter transformation. We pass all the rows from a source transformation through the Filter transformation, and then enter a Filter condition for the transformation. All ports in a Filter transformation are input/output and only rows that meet the condition pass through the Filter Transformation.

Example: to filter records where SAL>2000

• Import the source table EMP in Shared folder. If it is already there, then don’t Import.
• In shared folder, create the target table Filter_Example. Keep all fields as in EMP table.
• Create the necessary shortcuts in the folder.

Creating Mapping:

1. Open folder where we want to create the mapping.
2. Click Tools -> Mapping Designer.
3. Click Mapping -> Create -> Give mapping name. Ex: m_filter_example
4. Drag EMP from source in mapping.
5. Click Transformation -> Create -> Select Filter from list. Give name and click  Create. Now click done.
6. Pass ports from SQ_EMP to Filter Transformation.
7. Edit Filter Transformation. Go to Properties Tab
8. Click the Value section of the Filter condition, and then click the Open button.
9. The Expression Editor appears.
10. Enter the filter condition you want to apply.
11. Click Validate to check the syntax of the conditions you entered.
12. Click OK -> Click Apply -> Click Ok.
13. Now connect the ports from Filter to target table.
14. Click Mapping -> Validate
15. Repository -> Save

Create Session and Workflow as described earlier. Run the workflow and see the data in target table.

How to filter out rows with null values?

To filter out rows containing null values or spaces, use the ISNULL and IS_SPACES Functions to test the value of the port. For example, if we want to filter out rows that  Contain NULLs in the FIRST_NAME port, use the following condition:

IIF (ISNULL (FIRST_NAME), FALSE, TRUE)

This condition states that if the FIRST_NAME port is NULL, the return value is FALSE and the row should be discarded. Otherwise, the row passes through to the next Transformation.

Performance tuning:

Filter transformation is used to filter off unwanted fields based on conditions we Specify.

1. Use filter transformation as close to source as possible so that unwanted data gets Eliminated sooner.
2. If elimination of unwanted data can be done by source qualifier instead of filter,Then eliminate them at Source Qualifier itself.
3. Use conditional filters and keep the filter condition simple, involving TRUE/FALSE or 1/0