Maintain Derived Fields
Derived fields are supported by certain connectors that come out-of-the-box in Composer. To see what connectors support derived fields and what functions are available, see Connector Feature Support and Row-Level Functions.
A derived field is an in-memory column for your data table that is populated with results from calculations performed on data already in your table. You can create derived fields using row-level expressions that are built using row-level functions.
These calculations are performed at the level of a row, that is, a record, and do not include other data from your table that is outside of that particular row. If a source supports derived fields, then you can use them as arguments for aggregate functions when creating other calculations.
Derived fields can be created from other derived fields.
Consider the following examples:
Your data source has records that list the revenue generated and the term of employment but does not have an average of the two. You can use a derived field to create an average of the two for each record. Use the following formula:
Your data source continues values that have been brought in as text strings. In order to cross-reference this data with the time values, you need to change the text to a numeric value. Use the following formula as a base:
TEXT_TO_NUM (LTRIM (Field_A, '$')) SUM(TEXT_TO_NUM(SUBSTRING("$124456.00", 2, 10)))
Your data source contains records that list the start of employment and termination of employment for your company. You want to find the differences between these time values to average out the length of employment. Use the following formula as a base:
TIME_DIFF (timePart, startTime : Time, endTime : Time) : Numeric
Composer supports row-level functions in derived fields. See Row-Level Functions.
Derived fields can be hidden. See Hiding Fields.
For information on maintaining derived fields, see the following links:
- Derived Field Editor
- Creating and Modifying Derived Fields
- Duplicating Derived Fields
- Row-Level Functions
- Deleting Derived Fields
- Hiding Fields