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====== Data Operation - Select (Selection) ======


===== About =====
''select'' is a [[:docs:flow:supplier|supplier]] [[docs:op:op|data operation]] that selects [[docs:resource:resource|data Resources]].



<note important>
This is not the [[docs:resource:sql_select|sql select statement]]. The [[docs:resource:sql_select|sql select statement]] selects [[docs:resource:record|records]] while the ''select'' operation selects [[docs:resource:resource|Data Resources]].
</note>

<note info>
See the following ''learning guide'' page, to known more: [[howto:getting_started:4_select_data_resources]]
</note>







===== Arguments =====
The ''select'' operations has the following arguments.

^ Argument ^ Default ^ Description ^
| [[docs:flow:data_selector|data-selector]] | - | Select [[docs:resource:resource|data resources]] by [[:docs:common:globbing|glob pattern]] |
| [[docs:flow:data_selector|data-selectors]] | - | A list of [[docs:flow:data_selector|data-selectors]] |
| [[docs:op:with-dependencies|with-dependencies]] | false | If set to true, the [[docs:resource:dependency|dependencies]] will be added |
| ''data-def'' | Optional | The [[docs:resource:attribute|data attributes]] defined in a [[:docs:resource:data-definition|data definition]] format |
| ''logical-name'' | Optional | A [[:docs:conf:template|template logical name]] |
| ''media-type'' | Optional, detected by default | The [[docs:resource:media-type|media type]] of the selected resources |
| ''order'' | Natural | The order in which the data resources are returned. Possible value: `natural`, `drop`, `create` (Note that the ''order'' is by connection.) |
| ''processing-type'' | ''batch'' | The [[:docs:flow:processing-type|processing type]] (''batch'' or ''stream'') |
| ''strict-selection'' | false | If set to true, the ''select'' operation will throw an error if \\ * the selection does not return any data resource \\ * or any view is invalid |

When the processing type is ''stream'', the [[:docs:flow:stream_pipeline#attributes|stream attributes]] can be used


===== Usage =====

<tabs skin="tabs">
<tab panel="pipeline" selected="true">Flow</tab>
<tab panel="tabul" >Tabul Data Command</tab>
</tabs>
<tabpanels>
<tabpanel id="pipeline">
In a [[docs:flow:pipeline|pipeline pipeline]], this is a first operation (known as the [[docs:flow:supplier|supplier operation]]) because it supplies [[docs:resource:resource|data resources]] to the others operations in the pipeline.

Example:
  * Simple selection:
<code yaml>
pipeline:
  - name: 'Select data resources'
    operation: select
    args:
      data-selector: pattern@connection
      with-dependency: (yes|no)
      strict-selection: yes
</code>
</tabpanel>
<tabpanel id="tabul">
In a [[docs:tabul:data:start|tabul data command]], you set :
  * the [[docs:flow:data_selector|data selector]] as argument
  * and the [[docs:op:with-dependencies|with-dependencies]] as [[docs:tabul:flag|flag]]
  * and the ''not-strict'' as [[docs:tabul:flag|flag]]

Example:
<code bash>
tabul data command [--not-strict] [--with-dependency] dataSelector
</code>

You can verify the selected data resources with the [[:docs:tabul:data:list|tabul data list command]].
</tabpanel>
</tabpanels>


===== Note on Empty Selection =====

If no ''data resource'' matched the [[docs:flow:data_selector|data selector]], this is not considered an error.
This is already the case for all sql statement (ie an update that does not match a row does not return an error)

If you want to throw an error, you should set the ''strict-selection'' option to true.