---json
{
    "page_id": "iu6rjwh16qbkkrmun10f0"
}
---
====== Data Resource - Virtual Columns ======


===== About =====
''virtual columns'' are [[column|columns]] that contains generated data by [[:docs:generator:data-supplier|data supplier]].


===== Usage =====

They are most used to:
  * add [[:docs:resource:attribute|data attributes]] from the [[:docs:resource:resource|data resource]] such as its [[docs:resource:name|name]], its [[docs:resource:size|size]] or its [[docs:resource:count|count]] (via with the [[:docs:generator:meta|meta supplier]])
  * or to compute ''expression'' with the [[:docs:generator:expression|expression data supplier]]


===== How to add virtual columns? =====


''Tabulify'' permits to add virtual columns with:
  * the [[#enrich operation]]
  * the ''virtual-column'' [[docs:tabul:option|tabul option]].


==== Enrich Operation ====

[[docs:op:enrich|Enrich]] is a intermediate pipeline operation that accepts all [[:docs:generator:data-supplier|data suppliers]] as value source.



==== virtual-column tabul option ====
The ''virtual-column'' [[docs:tabul:option|tabul option]] is a short cut to add a virtual column based only on the [[:docs:generator:meta|meta supplier]]

The syntax is the following:
<code>
--virtual-column "virtualColumnName=dataResourceAttributeName"
</code>
where:
  * ''virtualColumnName'' is the name of the column added
  * ''dataResourceAttributeName'' is the name of [[docs:resource:attribute|data resource attribute]].