August 17, 2023

tWaitForSqlData – Docs for ESB 5.x



tWaitForSqlData properties

Component family




tWaitForSqlData component
iterates on a given connection for insertion or deletion of rows and
triggers a subjob to be executed when the condition is met.


This component allows a subjob to be triggered given a condition
linked to SQL data presence.

Basic settings

Wait at each iteration (in seconds)

Set the time interval in seconds between each check for the sql


Max. iterations (infinite if empty)

Number of checks for sql data before the Jobs times out.


Use an existing connection/Component List

A connection needs to be open to allow the loop to check for sql
data on the defined DB.


When a Job contains the parent Job and the child Job,
Component list presents
only the connection components in the same Job level, so if you
need to use an existing connection from the other level, you

From the available database connection component in the level
where the current component is, select the Use or register a shared DB connection check
box. For more information about this check box, see Databases – traditional components, Databases – appliance/datawarehouse components, or Databases – other components for the connection components
according to the database you are using.

Otherwise, still in the level of the current component,
deactivate the connection components and use Dynamic settings of the component to
specify the intended connection manually. In this case, make
sure the connection name is unique and distinctive all over
through the two Job levels. For more information about Dynamic settings, see Talend Studio User


Table to scan

Name of the table to be checked for insert or deletion


Trigger action when rowcount is

Select the condition to be met for the action to be carried

Equal to
Not Equal to
Greater than
Lower than
Greater or equal to
Lower or equal to



Define the value to take into account.



Select the action to be carried out: either stop the iterations
when the condition is met (exit
or continue the loop until the end of the max
iteration number (continue

Global Variables

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.

CURRENT_ITERATION: the sequence number of the current
iteration. This is a Flow variable and it returns an integer.

ROW_COUNT: the number of rows detected in the table. This
is a Flow variable and it returns an integer.

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 +
to access the variable list and choose the variable to use from it.

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


Although this component requires a Connection component to open
the DB access, it plays also the role of the start (or trigger)
component of the subjob which gets executed under the condition
described. Therefore this component requires a subjob to be
connected to via an Iterate link.



Scenario: Waiting for insertion of rows in a table

This scenario describes a Job reading a DB table and waiting for data to be put in
this table in order for a subjob to be executed. When the condition of the data
insertion in the table is met, then the subjob performs a Select* on the table and
simply displays the content of the inserted data onto the standard console.

  • Drop the following components from the Palette onto the design workspace: tMySqlConnection, tWaitForSqlData, tMysqlInput,

  • Connect the tMysqlConnection component to the
    tWaitforSqlData using an OnSubjobOK link, available on the right-click

  • Then connect the tWaitForSqlData component to
    the subjob using an Iterate link as no actual
    data is transferred in this part. Indeed, simply a loop is implemented by the
    tWaitForSqlData until the condition is

  • On the subjob to be executed if the condition is met, a tMysqlInput is connected to the standard console component,
    tLogRow. As the connection passes on data,
    use a Row main link.

  • Now, set the connection to the table to check at regular intervals. On the
    Basic Settings view of the tMySqlConnection
    Component tab, set the DB connection

  • Fill out the Host, Port, Database, Username, Password
    fields to open the connection to the Database table.

  • Select the relevant Encoding if

  • Then select the tWaitForSqlData component,
    and on the Basic Setting view of the Component tab, set its properties.

  • In the Wait at each iteration field, set the
    time in seconds you want to wait before the next iteration starts.

  • In the Max iterations field, fill out the
    number of iterations max you want to have before the whole Job is forced to

  • The tWaitForSqlData component requires a
    connection to be open in order to loop on the defined number of iteration.
    Select the relevant connection (if several) in the Component List combo box.

  • In the Table to scan field, type in the name
    of the table in the DB to scan.In this example:

  • In the Trigger action when rowcount is and
    Value fields, select the condition to be
    met, for the subjob to be triggered. In this use case, the number of rows in the
    scanned table should be greater or equal to 1.

  • In the Then field, select the action to be
    carried out when the condition is met before the number of iteration defined is
    reached. In this use case, as soon as the condition is met, the loop should be

  • Then set the subjob to be executed when the condition set is met. In this use
    case, the subjob simply selects the data from the scanned table and displays it
    on the console.

  • Select the tMySqlInput component, and on the
    Basic Setting view of the Component tab, set the connection to the

  • If the connection is set in the Repository, select the relevant entry on the
    list. Or alternatively, select the Use an existing
    check box and select the relevant connection component
    on the list.

  • In this use case, the schema corresponding to the table structure is stored in
    the Repository.

  • Fill out the Table Name field with the table
    the data is extracted from, Test_datatypes.

  • Then in the Query field, type in the Select
    statement to extract the content from the table.

  • No particular setting is required in the tLogRow component for this use case.

Then before executing the Job, make sure the table to scan
(test_datatypes) is empty, in order for the condition (greater
or equal to 1) to be met. Then execute the Job by pressing the F6 key on your keyboard. Before the end of the iterating loop, feed the
test_datatypes table with one or more rows in order to meet the condition.


The Job ends when this table insert is detected during the loop, and the table content
is thus displayed on the console.


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