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====== Data Operation - Create ======

===== About =====
''create'' is an [[:docs:flow:intermediate|intermediate operation]] that creates the [[docs:resource:metadata|metadata]] (ie [[docs:resource:structure|structure]], ...) from its [[:docs:flow:input|inputs]] (ie [[docs:resource:resource|data resource]])

<note>
  * This operation does not create any data. It creates only the [[docs:resource:metadata|metadata]].
</note>


===== Create vs SQL DDL Create =====

This operation is not [[:docs:resource:sql_ddl|DDL CREATE statement]].

This operation can:
    * create by metadata copy of its inputs
    * and optionally create a view from a [[:docs:resource:sql_select|select input]]


If you want to use the ''SQL DDL CREATE statement'', you need to create and execute a [[:docs:resource:sql_ddl|SQL DDL Query]]


===== Howto =====

The [[docs:tabul:data:create|data create command]] gives you access to the ''create'' operation to create resources.

Howto that are using the [[:docs:tabul:data:create|tabul create command]]:
  * [[:howto:sql_view:create_from_select]]
  * [[:howto:sql_table:create_table]]
  * [[:howto:sql_schema:create_table_with_dependencies]]
===== Usage =====

==== Creation By Selection ====

When you use the [[docs:op:select|select operation as supplier]] (ie when you select your resources), the ''create'' operation will apply the following `create` actions:

^ Create Action ^ target-data-uri \\ argument ^ target-media-type \\ argument ^ Inputs Expected ^
| Creation by [[docs:resource:metadata|metadata]] copy | Mandatory | Optional | All data resources expect [[docs:resource:runtime|runtime resources]] |
| Create view as | Mandatory | [[docs:resource:sql_view|sql view]] | [[docs:resource:sql_select|sql select query]] |






==== Creation By Definition ====

When you use the [[docs:op:define|define operation as supplier]] (ie when you [[docs:op:define|define]] your data resources), the ''create'' operation will apply the following `create` actions:

^ Action ^ ''target-data-uri'' ^
| In-place creation | Null |
| Out-of-place creation (by [[docs:resource:metadata|metadata]] copy) | Not null |

===== Arguments =====


^ Name ^ Default ^ Description ^
| ''target-data-uri'' | See [[#usage]] | A [[:docs:flow:template_data_uri|template data uri]] that defines where the data resources should be created. |
| ''target-media-type'' | Optional | The ''target'' [[:docs:resource:media-type|media type]] that defines the data type of resource created. \\ Derived from the `target-data-uri` if empty |
| ''target-data-def'' | Optional | Metadata applied to the created resources (ie target) specified in a [[:docs:resource:data-definition|data definition format]] |
| ''processing-type'' | ''batch'' | The [[:docs:flow:processing-type|processing type]] |
| ''output'' | ''results'' | The [[:docs:flow:output|outputs]] type. One of: ''results'', ''inputs'', ''targets'' |


==== Results Output Type ====

The results output type is a [[:docs:resource:tabular|tabular resource]] with 2 columns:
  * the ''input''
  * the ''target''


===== Cli =====

The [[docs:tabul:data:create|data create command]] gives you access to the ''create'' operation to create resources.

===== Note =====

==== How to copy data resource with foreign keys? ====

In [[:docs:flow:processing-type|Batch processing]], the ''create'' operation will also copy the [[:docs:generator:foreign_key|foreign keys]] of data resource in the batch.

If you want to create a ''star schema'', you can specify in the [[:docs:op:select|select operation]] to take the foreign table with the ''-with-dependencies'' option. Example: [[:howto:sql_schema:create_table_with_dependencies]]
==== Empty but Size not null ====

The created resources are ''empty'' but may have a [[:docs:resource:size|size]] not null.

Why? Some resource stores their metadata close to their data.

For instance, a [[:docs:resource:csv|csv]] has headers that will count toward the size.

==== Other operations that creates data resources ====

  * By default, any [[:docs:op:transfer|transfer operations]] will create the [[docs:flow:target|target data resource]] from its input  if it does not exist
  * The [[template|template operation]] will also create data resources.