Derived Column Transformation
The Derived Column transformation creates new column values by applying expressions to transformation input columns. An expression can contain any combination of variables, functions, operators, and columns from the transformation input. The result can be added as a new column or inserted into an existing column as a replacement value. The Derived Column transformation can define multiple derived columns, and any variable or input columns can appear in multiple expressions.
You can use this transformation to perform the following tasks:
Concatenate data from different columns into a derived column. For example, you can combine values from the FirstName and LastName columns into a single derived column named FullName, by using the expression
FirstName + " " + LastName.
Extract characters from string data by using functions such as SUBSTRING, and then store the result in a derived column. For example, you can extract a person's initial from the FirstName column, by using the expression
Apply mathematical functions to numeric data and store the result in a derived column. For example, you can change the length and precision of a numeric column, SalesTax, to a number with two decimal places, by using the expression
Create expressions that compare input columns and variables. For example, you can compare the variable Version against the data in the column ProductVersion, and depending on the comparison result, use the value of either Version or ProductVersion, by using the expression
ProductVersion == @Version? ProductVersion : @Version.
Extract parts of a datetime value. For example, you can use the GETDATE and DATEPART functions to extract the current year, by using the expression
Convert date strings to a specific format using an expression.
Configuration of the Derived Column Transformation
You can configure the Derived column transformation in the following ways:
Provide an expression for each input column or new column that will be changed. For more information, see Integration Services (SSIS) Expressions.
If an expression references an input column that is overwritten by the Derived Column transformation, the expression uses the original value of the column, not the derived value.
If adding results to new columns and the data type is string, specify a code page. For more information, see Comparing String Data.
The Derived Column transformation includes the FriendlyExpression custom property. This property can be updated by a property expression when the package is loaded. For more information, see Use Property Expressions in Packages, and Transformation Custom Properties.
This transformation has one input, one regular output, and one error output.
You can set properties through SSIS Designer or programmatically.
The Advanced Editor dialog box reflects the properties that can be set programmatically. For more information about the properties that you can set in the Advanced Editor dialog box or programmatically, click one of the following topics:
For more information about how to set properties, click one of the following topics:
Derived Column Transformation Editor
Use the Derived Column Transformation Editor dialog box to create expressions that populate new or replacement columns.
Variables and Columns
Build an expression that uses a variable or an input column by dragging the variable or column from the list of available variables and columns to an existing table row in the pane below, or to a new row at the bottom of the list.
Functions and Operators
Build an expression that uses a function or an operator to evaluate input data and direct output data by dragging functions and operators from the list to the pane below.
Derived Column Name
Provide a derived column name. The default is a numbered list of derived columns; however, you can choose any unique, descriptive name.
Select a derived column from the list. Choose whether to add the derived column as a new output column, or to replace the data in an existing column.
Type an expression or build one by dragging from the previous list of available columns, variables, functions, and operators.
The value of this property can be specified by using a property expression.
If adding data to a new column, the Derived Column TransformationEditor dialog box automatically evaluates the expression and sets the data type appropriately. The value of this column is read-only. For more information, see Integration Services Data Types.
If adding data to a new column, the Derived Column TransformationEditor dialog box automatically evaluates the expression and sets the column length for string data. The value of this column is read-only.
If adding data to a new column, the Derived Column TransformationEditor dialog box automatically sets the precision for numeric data based on the data type. The value of this column is read-only.
If adding data to a new column, the Derived Column TransformationEditor dialog box automatically sets the scale for numeric data based on the data type. The value of this column is read-only.
If adding data to a new column, the Derived Column TransformationEditor dialog box automatically sets code page for the DT_STR data type. You can update Code Page.
Configure error output
Specify how to handle errors by using the Configure Error Output dialog box.
Technical article, SSIS Expression Examples, on social.technet.microsoft.com