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====== Learning Tabulify - Step 4 - How to select Data Resources ======


===== Concepts =====

To [[docs:op:select|select a data resources]] such as a [[docs:resource:file|file]] or a [[docs:resource:sql_table|database table]], ''Tabulify'' uses the concept of:
  * [[#data selector]]
  * and [[#selection_with_dependencies|dependency]] (Do we select also the dependent ''data resources'')

This page goes through this concepts with explanation and examples.

===== Data Selector =====


A ''data selector'' is composed of two parts:
  * a [[docs:common:globbing|glob pattern]]
  * and a [[docs:connection:connection|connection]]
  * separated by the ''@'' (at) sign.

A [[docs:flow:data_selector|data selector]] looks like that:
<code>
globPattern@connection
</code>

A [[docs:common:globbing|glob pattern]] permits to define the ''name'' or the ''path'' of the [[docs:resource:resource|data resource]] located in its [[docs:connection:connection#system|system connection]].


===== Normal Selection =====

For instance, with the [[docs:system:tpcds|internal TPC-DS data store]], the below [[docs:tabul:data:list|list command]] will select all [[docs:resource:sql_table|tables]] that ends with the term ''sales'' because the ''*'' character matches all characters.
<unit>
<code bash>
tabul data list *sales@tpcds
</code>
where:
  * ''tabul'' is the [[docs:tabul:tabul|main command line utility]]
  * ''data'' is a [[docs:tabul:module|module]] (ie the [[docs:tabul:data:start|data module]])
  * ''list'' is a [[docs:tabul:command|command]]
  * ''*sales@tpcds'' is a [[docs:flow:data_selector|resource data selector]] that select [[docs:resource:resource|data resources]].
      * ''tpcds'' defines the [[docs:connection:connection|connection]]
      * ''*sales'' defines the [[docs:resource:sql_table|tables]] to look for with a [[docs:common:globbing|glob pattern]]. In our case all tables that finish with the word ''sales'' because  ''*'' is the [[docs:common:globbing|globbing star]] and select all characters.

Output:
<console>
path            media_type
-------------   ------------
catalog_sales   sql/relation
store_sales     sql/relation
web_sales       sql/relation
</console>
</unit>

<note>
To get more practice on ''glob pattern'', you can have a look at this page. [[howto:tabul:glob]]
</note>


===== Selection with dependencies =====

When moving data due to [[docs:resource:fkey|foreign-key constraint]], you need to move the data resources and their [[docs:resource:dependency|dependencies]].

That's why ''Tabulify'' offers the  ''%%--with-dependencies%%'' [[docs:tabul:flag|flag]] that will select also the [[docs:resource:dependency|dependent resources]] of the selected [[docs:resource:resource|data resource]]

Example: All ''tables'' that have a name that ends with ''sales'' in the [[docs:system:tpcds|tpcds system]] and their [[docs:resource:dependency|dependent tables]]
<unit>
<code bash>
tabul data list --with-dependencies *sales@tpcds
</code>

<console>
path                     media_type
----------------------   ------------
call_center              sql/relation
catalog_page             sql/relation
catalog_sales            sql/relation
customer                 sql/relation
customer_address         sql/relation
customer_demographics    sql/relation
date_dim                 sql/relation
household_demographics   sql/relation
income_band              sql/relation
item                     sql/relation
promotion                sql/relation
ship_mode                sql/relation
store                    sql/relation
store_sales              sql/relation
time_dim                 sql/relation
warehouse                sql/relation
web_page                 sql/relation
web_sales                sql/relation
web_site                 sql/relation
</console>
</unit>

===== Local File System =====
The connection part of a [[docs:flow:data_selector|data selector]] is not mandatory as the default connection is the [[docs:connection:cd|local file system]].

Therefore, performing the [[docs:tabul:data:list|list command]] with a [[docs:flow:data_selector|data selector]] without ''connection'' will give you a list of the file in your current directory.

<code bash>
tabul data list *
</code>
<console>
path
-----------------------
README.md
characters.csv
date_dim--generator.yml
sequence--generator.yml
</console>

<note>
This is then the equivalent of the [[wp>Ls|ls command]]
</note>

===== Next =====
Now that we know how to select [[docs:resource:resource|data resources]], the next page will show you how to print their content.

<btn>
[[5_print_data_resource|How to print Data Resources]]
</btn>