In Data Exchange, defining expressions for features refers to a basic mathematical and logical relationship added to the existing mapping from the source feature to the target feature. To transform multiple source features into a target feature, you must define expressions between them. You can also define expressions between one source feature and one target feature.
Expressions can also be defined for kanji features.
Note: Data Exchange does not support mapping of multiple RDMS columns to one target column. You can define an expression between one source column and one target column.
To define an expression
In the FeatureMap Designer, click the Expression icon (
), for the selected target feature. This icon
appears in the last column of the table view of the target features.The Expression dialog box appears.
To define an expression in the Expression Editor, double-click the required variables and functions. Alternatively, you can either drag or type the variables and functions.
Notes:
To manually type kanji names of the source variables, you should provide the input in Japanese; however, while typing the operators, you should provide the input in English. If you type the operators or functions in Japanese, the expression becomes invalid.
While defining an expression, if you manually type the variables, ensure to use the angular bracket (<) twice for a valid syntax. A single angular bracket (<) represents “less than”, and therefore, the expression is not validated.
In case of an Oracle database or a SQL Server database, Data Exchange treats the database as the target, which in turn can have many schemas. Different schemas can have tables with the same name. When tables with the same name are dragged into the ClassifierMap Designer, DDW differentiates the tables by prefixing the schema name to the table name. While defining a transformation in DDW, ensure that you have selected the table from the correct schema.
Click Validate to validate the expression.
If the validation is successful, a success notification appears. If the validation fails, an error message is displayed. Check the message for errors, and redefine the expression.
Click Save to save the expression.
If the expression is invalid, an error message is displayed. A warning message also appears. Click Yes to save the expression and close the window. Click No to close the warning message and redefine the expression.
To test the expression that you have defined
In the Evaluation pane, provide the required values in the Input area.
Note: If you enter invalid values, a warning sign appears adjacent to the input field.
Click Test to view the result in the Output area.
Note: The Test button is enabled only after the expression is validated successfully.
Click OK.
You can click Cancel to cancel the process.
Data Exchange provides system variables and three types of functions for defining expressions. Functions enable you to customize the data while transforming it from a particular source data store to a target data store.