tMysqlOutput

Writes, updates, makes changes or suppresses entries in a database.

tMysqlOutput executes the action defined on the table
and/or on the data contained in the table, based on the flow incoming from the preceding
component in the Job.

Depending on the Talend
product you are using, this component can be used in one, some or all of the following
Job frameworks:

Standard: see tMysqlOutput Standard properties.

The component in this framework is available in all Talend
products.
MapReduce: see tMysqlOutput MapReduce properties (deprecated).

The component in this framework is available in all subscription-based Talend products with Big Data
and Talend Data Fabric.
Spark Batch: see tMysqlOutput properties for Apache Spark Batch.

This component can also be used to write data to a RDS Aurora or a RDS MySQL
database.

The component in this framework is available in all subscription-based Talend products with Big Data
and Talend Data Fabric.
Spark Streaming: see tMysqlOutput properties for Apache Spark Streaming.

This component can also be used to write data to a RDS Aurora or a RDS MySQL
database.

This component is available in Talend Real Time Big Data Platform and Talend Data Fabric.

tMysqlOutput Standard properties

These properties are used to configure tMysqlOutput running in the Standard Job framework.

The Standard
tMysqlOutput component belongs to the Databases family.

The component in this framework is available in all Talend
products.

Note: This component is a specific version of a dynamic database
connector. The properties related to database settings vary depending on your database
type selection. For more information about dynamic database connectors, see Dynamic database components.

Basic settings

Database	Select a type of database from the list and click Apply.
Property type	Either Built-In or Repository. Built-In: No property data stored centrally. Repository: Select the repository file where the properties are stored.
DB Version	Select the MySQL version you are using.
	Click this icon to open a database connection wizard and store the database connection parameters you set in the component Basic settings view. For more information about setting up and storing database connection parameters, see Talend Studio User Guide.
Use an existing connection	Select this check box and in the Component List click the relevant connection component to reuse the connection details you already defined. Note: When a Job contains the parent Job and the child Job, if you need to share an existing connection between the two levels, for example, to share the connection created by the parent Job with the child Job, you have to: In the parent level, register the database connection to be shared in the Basic settings view of the connection component which creates that very database connection. In the child level, use a dedicated connection component to read that registered database connection. For an example about how to share a database connection across Job levels, see Talend Studio User Guide.
Host	Database server IP address.
Port	Listening port number of DB server.
Database	Name of the database.
Username and Password	DB user authentication data. To enter the password, click the […] button next to the password field, and then in the pop-up dialog box enter the password between double quotes and click OK to save the settings.
Table	Name of the table to be written. Note that only one table can be written at a time
Action on table	On the table defined, you can perform one of the following operations: Default: No operation is carried out. Drop and create a table: The table is removed and created again. Create a table: The table does not exist and gets created. Create a table if not exists: The table is created if it does not exist. Drop a table if exists and create: The table is removed if it already exists and created again. Clear a table: The table content is deleted. Truncate table: The table content is quickly deleted. However, you will not be able to rollback the operation.
Action on data	On the data of the table defined, you can perform: Insert: Add new entries to the table. If duplicates are found, the job stops. Update: Make changes to existing entries. Insert or update: Insert a new record. If the record with the given reference already exists, an update would be made. Update or insert: Update the record with the given reference. If the record does not exist, a new record would be inserted. Delete: Remove entries corresponding to the input flow. Replace: Add new entries to the table. If an old row in the table has the same value as a new row for a PRIMARY KEY or a UNIQUE index, the old row is deleted before the new row is inserted. Insert or update on duplicate key or unique index: Add entries if the inserted value does not exist or update entries if the inserted value already exists and there is a risk of violating a unique index or primary key. Insert Ignore: Add only new rows to prevent duplicate key errors. Warning: You must specify at least one column as a primary key on which the Update and Delete operations are based. You can do that by clicking Edit Schema and selecting the check box(es) next to the column(s) you want to set as primary key(s). For an advanced use, click the Advanced settings view where you can simultaneously define primary keys for the update and delete operations. To do that: Select the Use field options check box and then in the Key in update column, select the check boxes next to the column name on which you want to base the update operation. Do the same in the Key in delete column for the deletion operation. Note: The dynamic schema feature can be used in the following modes: Insert; Update; Insert or update; Update or insert; Delete.
Schema and Edit schema	A schema is a row description. It defines the number of fields (columns) to be processed and passed on to the next component. When you create a Spark Job, avoid the reserved word `line` when naming the fields. This component offers the advantage of the dynamic schema feature. This allows you to retrieve unknown columns from source files or to copy batches of columns from a source without mapping each column individually. For further information about dynamic schemas, see Talend Studio User Guide. This dynamic schema feature is designed for the purpose of retrieving unknown columns of a table and is recommended to be used for this purpose only; it is not recommended for the use of creating tables.
	Built-In: You create and store the schema locally for this component only.
	Repository: You have already created the schema and stored it in the Repository. You can reuse it in various projects and Job designs. When the schema to be reused has default values that are integers or functions, ensure that these default values are not enclosed within quotation marks. If they are, you must remove the quotation marks manually. You can find more details about how to verify default values in retrieved schema in Talend Help Center (https://help.talend.com).
	Click Edit schema to make changes to the schema. If the current schema is of the Repository type, three options are available: View schema: choose this option to view the schema only. Change to built-in property: choose this option to change the schema to Built-in for local changes. Update repository connection: choose this option to change the schema stored in the repository and decide whether to propagate the changes to all the Jobs upon completion. If you just want to propagate the changes to the current Job, you can select No upon completion and choose this schema metadata again in the Repository Content window.
Die on error	This check box is selected by default. Clear the check box to skip the row in error and complete the process for error-free rows. If needed, you can retrieve the rows in error via a Row > Rejects link.
Specify a data source alias	Select this check box and specify the alias of a data source created on the Talend Runtime side to use the shared connection pool defined in the data source configuration. This option works only when you deploy and run your Job in Talend Runtime . Warning: If you use the component’s own DB configuration, your data source connection will be closed at the end of the component. To prevent this from happening, use a shared DB connection with the data source alias specified. This check box is not available when the Use an existing connection check box is selected.

Advanced settings

Use alternate schema	Select this option to use a schema other than the one specified by the component that establishes the database connection (that is, the component selected from the Component list drop-down list in Basic settings view). After selecting this option, provide the name of the desired schema in the Schema field. This option is available when Use an existing connection is selected in Basic settings view.
Additional JDBC parameters	Specify additional connection properties for the DB connection you are creating. This option is not available if you have selected the Use an existing connection check box in the Basic settings. Note: You can press Ctrl+Space to access a list of predefined global variables.
Extend Insert	Select this check box to carry out a bulk insert of a defined set of lines instead of inserting lines one by one. The gain in system performance is considerable. Number of rows per insert: enter the number of rows to be inserted per operation. Note that the higher the value specified, the lower performance levels shall be due to the increase in memory demands. Note: This option is not compatible with the Reject link. You should therefore clear the check box if you are using a Row > Rejects link with this component. Warning: If you are using this component with tMysqlLastInsertID, ensure that the Extend Insert check box in Advanced Settings is not selected. Extend Insert allows for batch loading, however, if the check box is selected, only the ID of the last line of the last batch will be returned.
Use Batch	Select this check box to activate the batch mode for data processing. Note: This check box is available only when you have selected, the Update or the Delete option in the Action on data field.
Batch Size	Specify the number of records to be processed in each batch. This field appears only when the Use batch mode check box is selected.
Commit every	Number of rows to be included in the batch before it is committed to the DB. This option ensures transaction quality (but not rollback) and, above all, a higher performance level.
Additional Columns	This option is not available if you have just created the DB table (even if you delete it beforehand). This option allows you to call SQL functions to perform actions on columns, provided that these are not insert, update or delete actions, or actions that require pre-processing.
	Name: Type in the name of the schema column to be altered or inserted.
	SQL expression: Type in the SQL statement to be executed in order to alter or insert the data in the corresponding column.
	Position: Select Before, Replace or After, depending on the action to be performed on the reference column.
	Reference column: Type in a reference column that tMySqlOutput can use to locate or replace the new column, or the column to be modified.
Use field options	Select this check box to customize a request, particularly if multiple actions are being carried out on the data.
Use Hint Options	Select this check box to activate the hint configuration area which helps you optimize a query’s execution. In this area, parameters are: – HINT: specify the hint you need, using the syntax `/+ /`. – POSITION: specify where you put the hint in a SQL statement. – SQL STMT: select the SQL statement you need to use.
Debug query mode	Select this check box to display each step during processing entries in a database.
Use duplicate key update mode insert	Updates the values of the columns specified, in the event of duplicate primary keys.: Column: Between double quotation marks, enter the name of the column to be updated. Value: Enter the action you want to carry out on the column. Note: To use this option you must first of all select the Insert mode in the Action on data list found in the Basic Settings view.
tStatCatcher Statistics	Select this check box to collect log data at the component level.
Enable parallel execution	Select this check box to perform high-speed data processing, by treating multiple data flows simultaneously. Note that this feature depends on the database or the application ability to handle multiple inserts in parallel as well as the number of CPU affected. In the Number of parallel executions field, either: Enter the number of parallel executions desired. Press Ctrl + Space and select the appropriate context variable from the list. For further information, see Talend Studio User Guide. Note that when parallel execution is enabled, it is not possible to use global variables to retrieve return values in a subjob. Warning: The Action on table field is not available with the parallelization function. Therefore, you must use a tCreateTable component if you want to create a table. When parallel execution is enabled, it is not possible to use global variables to retrieve return values in a subjob.

Global Variables

Global Variables	NB_LINE: the number of rows read by an input component or transferred to an output component. This is an After variable and it returns an integer. NB_LINE_UPDATED: the number of rows updated. This is an After variable and it returns an integer. NB_LINE_INSERTED: the number of rows inserted. This is an After variable and it returns an integer. NB_LINE_DELETED: the number of rows deleted. This is an After variable and it returns an integer. NB_LINE_REJECTED: the number of rows rejected. This is an After variable and it returns an integer. QUERY: the query statement processed. This is an After variable and it returns a string. 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. A Flow variable functions during the execution of a component while an After variable functions after the execution of the component.

NB_LINE: the number of rows read by an input component or
transferred to an output component. This is an After variable and it returns an
integer.

NB_LINE_UPDATED: the number of rows updated. This is an
After variable and it returns an integer.

NB_LINE_INSERTED: the number of rows inserted. This is an
After variable and it returns an integer.

NB_LINE_DELETED: the number of rows deleted. This is an
After variable and it returns an integer.

NB_LINE_REJECTED: the number of rows rejected. This is an
After variable and it returns an integer.

QUERY: the query statement processed. This is an After
variable and it returns a string.

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.

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

Usage

Usage rule	This component offers the flexibility benefit of the DB query and covers all of the SQL queries possible. This component must be used as an output component. It allows you to carry out actions on a table or on the data of a table in a MySQL database. It also allows you to create a reject flow using a Row > Rejects link to filter data in error. For an example of tMySqlOutput in use, see Retrieving data in error with a Reject link.
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. The Dynamic settings table is available only when the Use an existing connection check box is selected in the Basic settings view. Once a dynamic parameter is defined, the Component List box in the Basic settings view becomes unusable. For examples on using dynamic parameters, see Reading data from databases through context-based dynamic connections and 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.

Usage rule

This component offers the flexibility benefit of the DB query and
covers all of the SQL queries possible.

This component must be used as an output component. It allows you to
carry out actions on a table or on the data of a table in a MySQL
database. It also allows you to create a reject flow using a Row > Rejects link to filter data in
error. For an example of tMySqlOutput
in use, see Retrieving data in error with a Reject link.

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.

The Dynamic settings table is
available only when the Use an existing
connection check box is selected in the Basic settings view. Once a dynamic parameter is
defined, the Component List box in the
Basic settings view becomes unusable.

For examples on using dynamic parameters, see Reading data from databases through context-based dynamic connections and 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.

Inserting a column and altering data using tMysqlOutput

This Java scenario is a three-component job that aims at creating random data using a
tRowGenerator, duplicating a column to be altered
using the tMap component, and eventually altering the
data to be inserted based on an SQL expression using the tMysqlOutput component.

Drop the following components from the Palette onto the design workspace: tRowGenerator, tMap and
tMySQLOutput.
Connect tRowGenerator, tMap, and tMysqlOutput using
the Row Main link.

In the design workspace, select tRowGenerator to display its Basic
settings view.

Click the Edit schema three-dot button to
define the data to pass on to the tMap
component, two columns in this scenario, name and
random_date.

Click OK to close the dialog box.
Click the RowGenerator Editor three-dot
button to open the editor and define the data to be generated.

Click in the corresponding Functions fields
and select a function for each of the two columns, getFirstName for
the first column and getrandomDate for the second column.
In the Number of Rows for Rowgenerator
field, enter 10 to generate ten first name rows and click Ok to close the editor.
Double-click the tMap component to open the
Map editor. The Map editor opens displaying the input metadata of the tRowGenerator component.

In the Schema editor panel of the Map
editor, click the plus button of the output table to add two rows and define the
first as random_date and the second as
random_date1.

In this scenario, we want to duplicate the random_date column and
adapt the schema in order to alter the data in the output component.

In the Map editor, drag the random_date row from the
input table to the random_date and random_date1
rows in the output table.

Click OK to close the editor.
In the design workspace, double-click the tMysqlOutput component to display its Basic settings view and set its parameters.

Set Property Type to Repository and then click the three-dot button to open the
Repository content dialog box and select
the correct DB connection. The connection details display automatically in the
corresponding fields.

Note:

If you have not stored the DB connection details in the Metadata entry in the Repository, select Built-in
on the property type list and set the connection detail manually.
Click the three-dot button next to the Table
field and select the table to be altered, Dates in this
scenario.
On the Action on table list, select
Drop table if exists and create, select
Insert on the Action on
data list.
If needed, click Sync columns to synchronize
with the columns coming from the tMap
component.
Click the Advanced settings tab to display
the corresponding view and set the advanced parameters.

In the Additional Columns area, set the
alteration to be performed on columns.

In this scenario, the One_month_later column replaces
random_date_1. Also, the data itself gets altered using
an SQL expression that adds one month to the randomly picked-up date of the
random_date_1 column. ex: 2007-08-12 becomes
2007-09-12.

-Enter One_Month_Later in the Name cell.

-In the SQL expression cell, enter the
relevant addition script to be performed, "adddate(Random_date, interval 1 month)" in this scenario.

-Select Replace on the Position list.

-Enter Random_date1 on the Reference column list.

Note:

For this job we duplicated the random_date_1 column in the DB
table before replacing one instance of it with the
One_Month_Later column. The aim of this workaround was to
be able to view upfront the modification performed.

Save your job and press F6 to execute
it.

The new One_month_later column replaces the
random_date1 column in the DB table and adds one month to each
of the randomly generated dates.

Updating data using tMysqlOutput

This Java scenario describes a two-component Job that updates data in a MySQL table
according to that in a delimited file.

Drop tFileInputDelimited and tMysqlOutput from the Palette onto the design workspace.
Connect the two components together using a Row
Main link.

Double-click tFileInputDelimited to display
its Basic settings view and define the
component properties.
From the Property Type list, select Repository if you have already stored the metadata of
the delimited file in the Metadata node in the
Repository tree view. Otherwise, select
Built-In to define manually the metadata of
the delimited file.

For more information about storing metadata, see
Talend Studio

User Guide.

In the File Name field, click the three-dot
button and browse to the source delimited file that contains the modifications
to propagate in the MySQL table.

In this example, we use the customer_update file that
holds four columns: id, CustomerName,
CustomerAddress and idState. Some
of the data in these four columns is different from that in the MySQL
table.

Define the row and field separators used in the source file in the
corresponding fields.
If needed, set Header, Footer and Limit.

In this example, Header is set to 1 since the
first row holds the names of columns, therefore it should be ignored. Also, the
number of processed lines is limited to 2000.
Click
the three-dot button next to Edit Schema to
open a dialog box where you can describe the data structure of the source
delimited file that you want to pass to the component that follows.

Select the Key check box(es) next to the
column name(s) you want to define as key column(s).

Note:

It is necessary to define at least one column as a key column for the Job to be
executed correctly. Otherwise, the Job is automatically interrupted and an error
message displays on the console.

In the design workspace, double-click tMysqlOutput to open its Basic
settings view where you can define its properties.

Click Sync columns to retrieve the schema of
the preceding component. If needed, click the three-dot button next to Edit schema to open a dialog box where you can check
the retrieved schema.
From the Property Type list, select Repository if you have already stored the connection
metadata in the Metadata node in the Repository tree view. Otherwise, select Built-In to define manually the connection
information.

For more information about storing metadata, see
Talend Studio

User Guide.
Fill in the database connection information in the corresponding
fields.
In the Table field, enter the name of the
table to update.
From the Action on table list, select the
operation you want to perform, Default in this
example since the table already exists.
From the Action on data list, select the
operation you want to perform on the data, Update in this example.
Save your Job and press F6 to execute it.

Using you DB browser, you can verify if the MySQL table, customers,
has been modified according to the delimited file.

In the above example, the database table has always the four columns
id, CustomerName,
CustomerAddress and idState, but certain
fields have been modified according to the data in the delimited file used.

Retrieving data in error with a Reject link

This scenario describes a four-component Job that carries out migration
from a customer file to a MySQL database table and redirects data in error towards a CSV
file using a Reject link.

In the Repository, select
the customer file metadata that you want to migrate and drop it onto the
workspace. In the Components dialog box,
select tFileInputDelimited and click
OK. The component properties will be
filled in automatically.
If you have not stored the information about your customer
file under the Metadata node in the
Repository. Drop a tFileInputDelimited component from the family
File > Input, in the Palette,
and fill in its properties manually in the Component tab.
From the Palette, drop a
tMap from the Processing family onto the workspace.
In the Repository, expand
the Metadata node, followed by the
Db Connections node and select the
connection required to migrate your data to the appropriate database. Drop it
onto the workspace. In the Components
dialog box, select tMysqlOutput and click
OK. The database connection
properties will be automatically filled in.
If you have not stored the database connection details under the
Db Connections node in the Repository, drop a tMysqlOutput from the Databases family in the Palette and fill in its properties manually in the Component tab.

For more information, see
Talend Studio

User Guide.

From the Palette, select
a tFileOutputDelimited from the
File > Output family, and drop it onto the workspace.
Link the customers
component to the tMap component, and the
tMap and Localhost with a Row
Main link. Name this second link out.
Link the Localhost to the
tFileOutputDelimited using a
Row > Reject link.
Double-click the customers component to display the Component view.

In the Property Type
list, select Repository and
click the […] button in order to
select the metadata containing the connection to your file. You can also select
the Built-in mode and fill in the fields
manually.
Click the […] button
next to the File Name field, and fill in
the path and the name of the file you want to use.
In the Row and Field Separator fields, type in between inverted
commas the row and field separator used in the file.
In the Header, Footer and Limit fields, type in the number of headers and footers to
ignore, and the number of rows to which processing should be limited.
In the Schema list, select
Repository and click the […] button in order to select the schema of
your file, if it is stored under the Metadata node in the Repository. You can also click the […] button next to the Edit
schema field, and set the schema manually.

The schema is as follows:

Double-click the tMap
component to open its editor.

Select the id, CustomerName, CustomerAddress, idSate, id2, RegTime and RegisterTime columns on the table on
the left and drop them on the out table,
on the right.

In the Schema editor
area, at the bottom of the tMap editor,
in the right table, change the length of the CustomerName column to 28 to create an
error. Thus, any data for which the length is greater than 28 will create
errors, retrieved with the Reject
link.
Click OK.
In the workspace, double-click the output Localhost component to display its Component view.

In the Property Type list,
select Repository and click the
[…] button to select the connection
to the database metadata. The connection details will be automatically filled
in. You can also select the Built-in mode
and set the fields manually.
In the Table field, type
in the name of the table to be created. In this scenario, we call it customers_data.
In the Action on data
list, select the Create table
option.
Click the Sync columns
button to retrieve the schema from the previous component.
Make sure the Die on
error check box isn’t selected, so that the Job can be executed
despite the error you just created.
Click the Advanced
settings tab of the Component view to set the advanced parameters of the
component.

Deselect the Extend
Insert check box which enables you to insert rows in batch,
because this option is not compatible with the Reject link.
Double-click the tFileOutputDelimited
component to set its properties in the Component view.

Click the […] button
next to the File Name field to fill in
the path and name of the output file.
Click the Sync columns
button to retrieve the schema of the previous component.
Save your Job and press F6 to execute it.

The data in error are sent to the delimited file, as well as the error
type met. Here, we have: Data truncation.

Writing dynamic columns from a source file to a database

This scenario applies only to subscription-based Talend products.

In this scenario, MySQL is used for demonstration purposes. You will read
dynamic columns from a source file, map them and then write them to a table in a MySQL database. By defining a dynamic column alongside known
column names, we can retrieve all of the columns from the source file, including the
unknown columns.

Drop a tFileInputDelimited, a
tMap and a tMysqlOutput component onto the workspace.

Link tFileInputDelimited to
tMap using a Row
> Main connection.
Link tMap to tMysqlOutput using a Row >
*New Output* (Main) connection.
Double-click tFileInputDelimited to open its Basic
Settings view in the Component
tab.

Warning:
The dynamic schema feature is only supported in Built-In mode.

Select Built-In from the
Property Type list.
Click the […] button next
to the File name/Stream field and browse to
the input file.
Enter the characters you want to use as separators next to the
Row Separator and Field Separator fields.
Click Edit Schema to define
the source file schema.

The Edit Schema dialog box
opens.

Add as many rows as required or delete rows using the and
buttons.
Modify the order of the columns using the and

buttons.
Under Column, enter the names
of each known column on separate rows.
In the last row, under Column, enter a name for the dynamic column.
Under Type, click the field
to define the type of data in the corresponding column.

Click the arrow to select the correct data type.

Warning:
Under Type, the dynamic column
type must be set as Dynamic.

Warning:
The dynamic column must be defined in the last row of the schema.

Click OK to close the dialog
box when you have finished defining the source schema.
Click tMap to open its
Basic Settings view in the Component tab.

Click […] next to
Map Editor to map the columns from the
source file.

On the toolbar on top of the Output
Panel on the top right of the window, click the button.

The Add an Output schema
dialog box appears.

Next to New output, enter a
name for the output schema.
Click OK to close the dialog
box.
Using the Ctrl + click
technique, highlight all off the column names in the input schema on the left and
drop them onto the output schema.

The columns dropped on the output columns retain their original
values and they are automatically mapped on a one to one basis.

In the output schema, click the relevant row under Expression if you want to use the Expression Builder to set advanced parameters for the
corresponding column in the output.
Click the […] button which
appears to open the Expression Builder and set
the parameters as required.

For further information about using the Expression Builder, see
Talend Studio

User Guide.

Warning:
The dynamic column must be mapped on a one to one basis and cannot
undergo any transformations. It cannot be used in a filter expression or in a
variables section. It cannot be renamed in the output table and cannot be used as a
join condition.

Click OK to close the
Map Editor.
Double click tMysqlOutput to
set its Basic Settings in the Component tab.

Select Built-in as the
Property Type.
Select the DB Version from
the corresponding list.
Next to Host, enter the
database server IP address.
Next to Port, enter the
listening port number of the database server.
Enter your authentication data in the Username and Password
fields.
Next to Action on table,
select the required action.
Next to Action on data,
select the required action.
Set the Schema type
as Built-in and click Edit schema to modify the schema if required.
Press F6 to run the Job.

The table is written to the MySQL database along with the data and
the column names of the previously unknown columns:

Note: The Job can also be run in the Traces
Debug mode, which allows you to view the rows as they are written to the
output file, in the workspace.

For further information about defining and mapping dynamic schemas, see
Talend Studio

User Guide.

For an example of how to write dynamic columns to an output file, see Writing dynamic columns from a database to an output file.