tMysqlColumnList - 6.3

Talend Components Reference Guide

EnrichVersion
6.3
EnrichProdName
Talend Big Data
Talend Big Data Platform
Talend Data Fabric
Talend Data Integration
Talend Data Management Platform
Talend Data Services Platform
Talend ESB
Talend MDM Platform
Talend Open Studio for Big Data
Talend Open Studio for Data Integration
Talend Open Studio for Data Quality
Talend Open Studio for ESB
Talend Open Studio for MDM
Talend Real-Time Big Data Platform
task
Data Governance
Data Quality and Preparation
Design and Development
EnrichPlatform
Talend Studio

Function

Iterates on all columns of a given table through a defined Mysql connection.

Purpose

Lists all column names of a given Mysql table.

tMysqlColumnList 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.

 

Table name

Enter the name of the table.

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 

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

DATA_TYPE: the data type of the column currently iterated upon. This is a Flow variable and it returns a string.

COLUMN_DEFAULT: the default value of the column currently iterated upon. This is a Flow variable and it returns a string.

IS_NULLABLE: nullability of the column currently uiterated upon. This is a Flow variable and it returns YES if the column allows NULL; otherwise, NO.

COLUMN_KEY: the key indicator of the column currently iterated upon. This is a Flow variable and it returns a string if the column is set to Key; otherwise it returns nothing.

CHARACTER_MAXIMUM_LENGTH: the maximum length in number of characters of the column currently iterated upon. This is a Flow variable, and it returns a numeric string for binary or character data types and NULL for other types.

NUMERIC_PRECISION: the data precision of the column currently iterated upon. This is a Flow variable, and it returns a numeric string for approximate numeric data, exact numeric data, integer data, or monetary data and NULL for other data types.

NUMERIC_SCALE: the scale in digits allowed in the column currently iterated upon. This is a Flow variable, and it returns a numeric string for approximate numeric data, exact numeric data, integer data, or monetary data and NULL for other data types.

NB_COLUMN: the number of columns iterated upon so far. This is an After 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 a DB table and listing its column names

The following Java scenario creates a five-component job that iterates on a given table name from a Mysql database using a Where clause and lists all column names present in the table.

  • Drop the following components from the Palette onto the design workspace: tMysqlConnection, tMysqlTableList, tMysqlColumnList, tFixedFlowInput, and tLogRow.

  • Connect tMysqlConnection to tMysqlTableList using an OnSubjobOk link.

  • Connect tMysqlTableList, tMysqlColumnList, and tFixedFlowInput using Iterate links.

  • Connect tFixedFlowInput to tLogRow using a Row Main link.

  • In the design workspace, select tMysqlConnection and click the Component tab to define its basic settings.

  • In the Basic settings view, set the database connection details manually or select them from the context variable list, through a Ctrl+Space click in the corresponding field if you have stored them locally as Metadata DB connection entries.

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

In this example, we want to connect to a Mysql database called customers.

  • In the design workspace, select tMysqlTableList and click the Component tab to define its basic 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 list on the console.

    In this scenario, the table we want to iterate on is called customer.

  • In the design workspace, select tMysqlColumnList and click the Component tab to define its basic settings.

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

  • In the Table name field, enter the name of the DB table you want to list its column names.

    In this scenario, we want to list the columns present in the DB table called customer.

  • In the design workspace, select tFixedFlowInput and click the Component tab to define its basic settings.

  • Set the Schema to Built-In and click the three-dot [...] button next to Edit Schema to define the data you want to use as input. In this scenario, the schema is made of two columns, the first for the table name and the second for the column name.

  • Click OK to close the dialog box, and accept propagating the changes when prompted by the system. The defined columns display in the Values panel of the Basic settings view.

  • Click in the Value cell for each of the two defined columns and press Ctrl+Space to access the global variable list.

  • From the global variable list, select ((String)globalMap.get("tMysqlTableList_1_CURRENT_TABLE")) and ((String)globalMap.get("tMysqlColumnList_1_COLUMN_NAME")) for the TableName and ColumnName respectively.

  • In the design workspace, select tLogRow.

  • Click the Component tab and define the basic settings for tLogRow as needed.

  • Save your job and press F6 to execute it.

The name of the DB table is displayed on the console along with all its column names.