August 16, 2023

tMemSQLInput – Docs for ESB 6.x

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tMemSQLInput

Executes a DB query with a strictly defined order which must correspond to the
schema definition.

tMemSQLInput connects to a given
database and extracts fields based on a user-defined query. Then it passes the selected data
to the next component via a Main row link.

tMemSQLInput Standard properties

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

The Standard
tMemSQLInput component belongs to the Big Data and the Databases families.

The component in this framework is available when you are using one of the Talend solutions with Big Data.

Basic settings

Property type

Either Built-in or
Repository
.

 

Built-in: No property data stored
centrally.

 

Repository: Select the repository
file in which the properties are stored. The fields that follow are
completed automatically using the data retrieved.

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:

  1. 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.

  2. 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

Enter the location of the server of the MemSQL database to be
used.

Port

Enter the listening port number of the server of the MemSQL
database to be used.

Database

Enter the name of the MemSQL database to be used.

Username and
Password

Enter the authentication data used to connect to the MemSQL
database to be used.

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. The schema is either Built-In or stored remotely in the Repository.

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. Related topic: see
Talend Studio

User Guide.

 

Repository: You have already created
the schema and stored it in the Repository. You can reuse it in various projects and
Job designs. Related topic: see
Talend Studio

User Guide.
 

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.

Table
Name

Name of the table to be read.

Query type and
Query

Enter your DB query paying particularly attention to properly
sequence the fields in order to match the schema definition.

If using the dynamic schema
feature, the SELECT query must include the * wildcard, to retrieve all of the columns from the table
selected.

Advanced settings

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:

When you need to handle data of the time-stamp type
0000-00-00 00:00:00 using this
component, set the parameter as:

noDatetimeStringSync=true&zeroDa­teTimeBehavior=convertToNull.

Trim all the String/Char columns

Select this check box to remove leading and trailing whitespace
from all the String/Char columns.

Trim column

Remove leading and trailing whitespace from defined
columns.

Note:

Clear Trim all the String/Char
columns to enable Trim columns in this
field.

tStatCatcher Statistics

Select this check box to collect log data at the component
level.

Global Variables

Global Variables 

NB_LINE: the number of rows processed. This is an After
variable and it returns an integer.

QUERY: the query statement being processed. This is a Flow
variable and it returns a string.

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

Usage rule

This component covers all possible SQL queries for MemSQL
databases.

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 Scenario: Reading data from 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.
Limitation

Due to license incompatibility, one or more JARs required to use this component are not
provided. You can install the missing JARs for this particular component by clicking the
Install button on the Component tab view. You can also find out and add all missing JARs easily on the
Modules tab in the
Integration
 perspective of your
studio. You can find more details about how to install external modules in Talend Help Center (https://help.talend.com).

Scenario: Writing data to and reading data from a MemSQL database table

This scenario applies only to a Talend solution with Big Data.

In this scenario a Job is built to write a table to a MemSQL database, and then
retrieve the data from the table.

Dragging and dropping components and linking them together

use_case-tmemsqlinput1.png

  1. Drop a tMemSQLConnection, a tRowGenerator, a tMemSQLInput, a tMemSQLOutput, a tMemSQLClose, and a tLogRow
    from the Palette onto the workspace.
  2. Link the tMemSQLConnection to the tRowGenerator using a Row >
    OnSubjobOk     connection.
  3. Link the tRowGenerator to the tMemSQLOutput using a Row >
    Main     connection.
  4. Link the tRowGenerator to the tMemSQLInput using a Row >
    OnSubjobOk     connection.
  5. Link the tMemSQLInput to the tLogRow using a Row > Main
    connection.
  6. Link the tMemSQLInput to the tMemSQLClose using a Row >
    OnSubjobOk     connection.

Configuring the components

Opening and closing connection to the database

  1. Double-click the tMemSQLConnection component to open its
    Basic settings in the Component tab.

    use_case-tmemsqlinput3.png

  2. In the Property Type list, select
    Built-In. Specify the connection
    details in the relevant fields, including the host name and listening port
    number of the database server, the user name and password for your database
    authentication, and the database name.
  3. Double-click tMemSQLClose to set its Basic settings in the Component tab.

    use_case-tmemsqlinput10.png

  4. The Component List is filled in automatically with
    tMemSQLConnection_1.

Writing data in a database table

  1. Double-click the tRowGenerator component
    to open the Row Generator editor.

    use_case-tmemsqlinput2.png

  2. Add three columns as shown below to generate 10 data
    rows:

    • id, Integer type, using
      Numeric.sequence from the
      Function list to generate
      sequence numbers.

    • firstName, String type, using TalendDataGenerator.getFirstName from the Function list to generate random first
      names.

    • lastName, String type, using
      TalendDataGenerator.getLastName
      from the Function list to generate
      random family names.

  3. In the Basic settings view of tRowGenerator in the Component tab, click the Edit
    Schema     button to open the schema editor. Set the length of
    the id, firstName, lastName
    column to 4, 10, and
    10.

    use_case-tmemsqlinput9.png

    When done, click OK to close the editor
    and click Yes when prompted to propagate
    the schema to the next component.
    For more information about how to configure the tRowGenerator component, see tRowGenerator.
  4. Double-click tMemSQLOutput to open its Basic Settings view in the Component tab.

    use_case-tmemsqlinput4.png

  5. Select the Use Existing Connection check
    box. The Component List is filled in
    automatically with tMemSQLConnection_1.

    Fill the Table field with the database
    table, customers in this example.
    Select Drop table if exists and create in
    the Action on table list, and Insert in the Action on
    table     list.

Reading data from a database table

  1. Double-click tMemSQLInput to open its Basic Settings view in the Component tab.

    use_case-tmemsqlinput5.png

  2. Select the Use Existing Connection check
    box. The Component List is filled in
    automatically with tMemSQLConnection_1.
  3. Set the Schema as Built-in and click Edit
    schema     to define the data structure of the database table to
    read data from.

    use_case-tmemsqlinput6.png

    Click the [+] button to add the rows that
    you will use to define the schema, three columns in this example
    id, firstName, and
    lastName.
    Under Column, click in the fields to enter the
    corresponding column names.
    Click the field under Type to define the type of
    data.
    Click OK to close the schema editor.
  4. Fill the Table field with the database
    table, customers in this example.

    Alternatively, click the […] button
    next to the Table Name field to select the
    database table of interest. A dialog box opens showing a tree diagram of all
    the tables in the selected database. Select customers
    and click OK to close the dialog
    box.
    use_case-tmemsqlinput7.png

  5. Set the Query Type as Built-In. Click the Guess
    Query     button. The Query box
    is filled in automatically to retrieve all columns from the selected table.
  6. Double-click tLogRow to set its Basic settings in the Component tab.

    use_case-tmemsqlinput8.png

  7. In the Mode area, select Table (print values in cells of a table) for a
    better display of the results.
  8. Save the Job.

Executing the Job

Press F6 to run the Job and see the results in the
console.

use_case-tmemsqlinput11.png

As shown above, the data with the desired column names is retrieved from the
database table.

Document get from Talend https://help.talend.com
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Docs 6.x
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