How to: Derive Column Values by Using the Derived Column Transformation
To add and configure a Derived Column transformation, the package must already include at least one Data Flow task and one source.
The Derived Column transformation uses expressions to update the values of existing or to add values to new columns. When you choose to add values to new columns, the Derived Column Transformation Editor dialog box evaluates the expression and defines the metadata of the columns accordingly. For example, if an expression concatenates two columns—each with the DT_WSTR data type and a length of 50—with a space between the two column values, the new column has the DT_WSTR data type and a length of 101. You can update the data type of new columns. The only requirement is that data type be compatible with the inserted data. For example, the Derived Column Transformation Editor dialog box generates a validation error when you assign a date value to a column with an integer data type. Depending on the data type that you selected, you can specify the length, precision, scale, and code page of the column.
To derive column values
In Business Intelligence Development Studio, open the Integration Services project that contains the package you want.
In Solution Explorer, double-click the package to open it.
Click the Data Flow tab, and then, from the Toolbox, drag the Derived Column transformation to the design surface.
Connect the Derived Column transformation to the data flow by dragging the connector—the green or red arrow—from the source or the previous transformation to the Derived Column transformation.
Double-click the Derived Column transformation.
In the Derived Column Transformation Editor dialog box, build the expressions to use as conditions by dragging variables, columns, functions, and operators to the Expression column in the grid. Alternatively, you can type the expression in the Expression column.
If the expression is not valid, the expression text appears in red and a ToolTip on the column describes the errors.
In the Derived Column list, select <add as new column> to write the evaluation result of the expression to a new column, or select an existing column to update with the evaluation result.
If you chose to use a new column, the Derived Column Transformation Editor dialog box evaluates the expression and assigns a data type to the column, depending on the data type, length, precisions, scale, and code page.
If using a new column, select a data type in the Data Type list. Depending on the selected data type, optionally update the values in the Length, Precision, Scale, and Code Page columns. Metadata of existing columns cannot be changed.
Optionally, modify the values in the Derived Column Name column.
To configure the error output, click Configure Error Output. For more information, see How to: Configure an Error Output in a Data Flow Component.
To save the updated package, click Save Selected Items on the File menu.