tMysqlTableList - 6.3

Talend Open Studio for Big Data Components Reference Guide

EnrichVersion
6.3
EnrichProdName
Talend Open Studio for Big Data
task
Data Governance
Data Quality and Preparation
Design and Development
EnrichPlatform
Talend Studio

Function

Iterates on a set of table names through a defined Mysql connection.

Purpose

Lists the names of a given set of Mysql tables using a select statement based on a Where clause.

tMysqlTableList Properties

Component family

Databases/MySQL

 

Basic settings

Component list

Select the tMysqlConnection component in the list if more than one connection are planned for the current job.

 

Where clause for table name selection

Enter the Where clause to identify the tables to iterate on.

Dynamic settings

Click the [+] button to add a row in the table and fill the Code field with a context variable to choose your database connection dynamically from multiple connections planned in your Job. This feature is useful when you need to access database tables having the same data structure but in different databases, especially when you are working in an environment where you cannot change your Job settings, for example, when your Job has to be deployed and executed independent of Talend Studio.

Once a dynamic parameter is defined, the Component List box in the Basic settings view becomes unusable.

For examples on using dynamic parameters, see Scenario 3: Reading data from MySQL databases through context-based dynamic connections and Scenario: Reading data from different MySQL databases using dynamically loaded connection parameters. For more information on Dynamic settings and context variables, see Talend Studio User Guide.

Global Variables 

CURRENT_TABLE: the name of the table currently iterated upon. This is a Flow variable and it returns a string.

NB_TABLE: the number of tables iterated upon so far. This is a Flow variable and it returns an integer.

ERROR_MESSAGE: the error message generated by the component when an error occurs. This is an After variable and it returns a string. This variable functions only if the Die on error check box is cleared, if the component has this check box.

A Flow variable functions during the execution of a component while an After variable functions after the execution of the component.

To fill up a field or expression with a variable, press Ctrl + Space to access the variable list and choose the variable to use from it.

For further information about variables, see Talend Studio User Guide.

Usage

This component is to be used along with Mysql components, especially with tMysqlConnection.

Log4j

If you are using a subscription-based version of the Studio, the activity of this component can be logged using the log4j feature. For more information on this feature, see Talend Studio User Guide.

For more information on the log4j logging levels, see the Apache documentation at http://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/Level.html.

Limitation

n/a

Scenario: Iterating on DB tables and deleting their content using a user-defined SQL template

The following Java scenario creates a three-component job that iterates on given table names from a MySQL database using a WHERE clause. It then deletes the content of the tables directly on the DBMS using a user-defined SQL template.

For advanced use, start with creating a connection to the database that contains the tables you want to empty of their content.

  • In the Repository tree view, expand Metadata and right click DB Connections to create a connection to the relevant database and to store the connection information locally.

    For more information about Metadata, see Talend Studio User Guide.

    Otherwise, drop a tMySQLConnection component in the design workspace and fill the connection details manually.

  • Drop the database connection you created from the Repository onto the design workspace.

    The [Components] dialog box displays.

  • Select tMysqlConnection and click OK.

    The tMysqlConnection components displays on the design workspace with all connection details automatically filled in its Basic settings view.

  • Drop the following two components from the Palette onto the design workspace: tMysqlTableList and tELT.

  • Connect tMysqlConnection to tMysqlTableList using an OnSubjobOk link.

  • Connect tMysqlTableList to tELT using an Iterate link.

  • If needed, double-click tMysqlConnection to display its Basic settings view and verify the connection details.

In this example, we want to connect to a MySQL database called examples.

  • In the design workspace, double-click tMysqlTableList to display its Basic settings view and define its settings.

  • On the Component list, select the relevant MySQL connection component if more than one connection is used.

  • Enter a WHERE clause using the right syntax in the corresponding field to iterate on the table name(s) you want to delete the content of.

    In this scenario, we want the job to iterate on all the tables which names start with "ex".

  • In the design workspace, double-click tELT to display its Basic settings view and define its settings.

  • In Database Name, enter the name of the database containing the tables you want to process.

  • On the Component list, select the relevant MySQL connection component if more than one connection is used.

  • Click in the Table name field and press Ctrl+Space to access the global variable list.

  • From the global variable list, select ((String)globalMap.get("tMysqlTableList_1_CURRENT_TABLE")).

To create the user-defined SQL template:

  • In the Repository tree view, expand SQL Templates and MySQL in succession.

  • Right-click UserDefined and select Create SQLTemplate from the drop-down list.

    The [New SQLTemplate] wizard opens.

  • Enter a name for the new SQL template and fill in the other fields If needed and then click Finish to close the wizard.

    An SQL pattern editor opens on the design workspace.

  • Delete the existing code and enter the code necessary to carry out the desired action, deleting the content of all tables which names start with "ex" in this example.

Note

In the SQL template code, you must use the correct variable name attached to the table name parameter ("__TABLE-NAME__" in this example). To display the variable name used, put your pointer in the Table Name field in the basic settings of the tELT component.

  • Press Ctrl+S to save the new user-defined SQL template.

The next step is to add the new user-defined SQL template to the SQL template list in the tELT component.

To add the user-defined SQL template to the SQL template list:

  • In the Component view of tELT, click the SQL Templates tab to display the SQLTemplate List.

  • Click the Add button and add two SQL template lines.

  • Click in the first line to display a drop-down arrow and then click the arrow to display the SQL template list.

  • Select in the list the user-defined SQL template you already created.

  • Make sure that the SQL template in the second line is Commit.

  • Save your job and press F6 to execute it.

All tables in the MySQL examples database which names begin with "ex" are emptied from their content.

Related scenario

For tMysqlTableList related scenario, see Scenario: Iterating on a DB table and listing its column names.