Maintain Derived Fields
This applies to: Visual Data Discovery
Derived fields are supported by certain connectors that come out-of-the-box in Symphony. To see what functions are available, see Supported Row-Level Functions.
Support for this feature by connector is shown in the following table.
Key:Y - Supported; N - Not Supported; N/A - not applicable
| Connector | Supported? | Notes |
|---|---|---|
Y |
|
|
Y |
|
|
Y |
|
|
Y |
Apache Phoenix and Apache Phoenix Query Server connectors support row-level expressions (derived fields) with the following limitations:
|
|
Y |
||
N |
|
|
Y |
If you need to access a BigQuery partition, explicitly include an alias for the built in partition column in your select clause, such as |
|
Y |
|
|
N |
|
|
Y |
|
|
N |
|
|
Y |
|
|
Y |
||
Y |
|
|
Y |
|
|
Y |
|
|
Y |
|
|
Y |
|
|
Y |
|
|
Y |
MongoDB connectors support derived fields with some exceptions. See the discussion in Manage the MongoDB Connector. |
|
Y |
|
|
Y |
|
|
Y |
|
|
Y |
|
|
N/A |
|
|
Y |
|
|
Y |
|
|
Y |
|
|
Y |
|
|
Y |
|
|
Y |
|
|
Y |
|
|
Y |
|
|
N |
|
|
Y |
|
|
Y |
|
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.
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:
(revenue/lengthofemployment)
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
Symphony supports row-level functions in derived fields. See Supported Row-Level Functions.
Derived fields can be hidden. See Hide Fields.
For information on maintaining derived fields, see the following links:
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