tMysqlColumnList

Iterates on all columns of a given Mysql table and lists column
names.

tMysqlColumnList Standard properties

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

The Standard
tMysqlColumnList component belongs to the Databases family.

The component in this framework is generally available.

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.

Advanced settings

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

Global Variables

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.

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

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

Usage rule

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

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: 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.

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.

Document get from Talend https://help.talend.com

Thank you for watching.

Docs 6.x

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tMysqlColumnList – Docs for ESB 6.x

tMysqlColumnList