Defining Expressions and Conditions FAQS

1. What are expressions and conditions used for?

• Expressions and conditions are used to map and transform attributes between components in a mapping process. They help define how data is manipulated, filtered, joined, or looked up within different components.

2. How do I edit an expression or condition?

• You can edit an expression or condition by selecting the target attribute in the mapping editor and modifying the corresponding field (Expression or Condition) in the Property Inspector. You can also use the Expression Editor for more advanced editing.

3. What happens if I manually edit an expression incorrectly?

• If you manually edit an expression and make an error (such as misspelling a source attribute), the cross-reference will become invalid. As a result, the source attribute will not be highlighted when clicking the target attribute.

4. What is the advantage of using the Expression Editor?

• The Expression Editor ensures that expressions have valid cross-references by allowing you to select source attributes directly. This minimizes errors and makes the editing process more efficient.

5. What is the difference between an expression and a condition?

• Expression: Used for data transformation or creating mappings in components like datastore, aggregate, and distinct components. They can have result types like VARCHAR or NUMERIC.
• Condition: Used for filtering, joining, or looking up data in components like filter, join, and lookup. Conditions always return a boolean value (TRUE or FALSE).

6. What is the "f" icon on an attribute in the logical diagram?

• The "f" icon indicates that a function (expression) has been applied to that attribute. It serves as a visual cue in the logical diagram to show which attributes have expressions attached to them.

7. How can I check if my mapping is correct after modifying expressions or conditions?

• After making changes to expressions or conditions, you can validate your mapping by clicking the green check mark icon in the top of the logical diagram. The system will check for errors such as empty expressions or missing connections.

8. Why aren't my source attributes appearing in the Expression Editor?

• If no attributes are appearing in the Expression Editor, it may be because your component has no upstream or downstream connections. Attributes are only listed if they are in scope (already connected to the component).

9. Can I use window functions in filter conditions?

• No, window functions are not valid in filter conditions. The condition must evaluate to a boolean result (TRUE or FALSE), and window functions do not meet this requirement.

10. What types of components use conditions?

• Conditions are primarily used in components like filter, join, and lookup (selector). These components require conditions to define how the data should be filtered, joined, or looked up.

11. What types of components use expressions?

• Expressions are used in components like datastore, aggregate, distinct, and projector components. They are essential for performing data transformations or mapping attributes.

12. Can I use multiple expressions on a single attribute?

• Yes, some components (like the Set component) can have multiple expressions on a single attribute. Other components, like most projectors, usually have one expression per attribute.

13. How do I know if my mapping is missing any connections?

• If your mapping is missing any connections between components, validation will alert you. The system will check if the input/output connectors are properly connected, and any missing connections will be flagged as errors.