Scenario 1: Aggregating table columns and filtering
This scenario describes a Job that gathers together several input DB table schemas and
implementing a clause to filter the output using an SQL statement.
Drop the following components from the Palette
onto the design workspace: three tELTMysqlInput
components, a tELTMysqlMap, and a tELTMysqlOutput. Label these components to best describe
Double-click the first tELTMysqlInput component
to display its Basic settings view.
Select Repository from the Schema list, click the three dot button preceding Edit schema, and select your DB connection and the
desired schema from the [Repository Content] dialog
The selected schema name appears in the Default Table
Name field automatically.
In this use case, the DB connection is
Talend_MySQL and the schema for the
first input component is owners.
Set the second and third tELTMysqlInput
components in the same way but select cars and
resellers respectively as their schema names.
In this use case, all the involved schemas are stored in the Metadata node of the Repository tree
view for easy retrieval. For further information concerning metadata, see
Talend Studio User Guide.
You can also select the three input components by dropping the relevant schemas from
the Metadata area onto the design workspace and
double-clicking tELTMysqlInput from the [Components] dialog box. Doing so allows you to skip the
steps of labeling the input components and defining their schemas manually.
Connect the three tELTMysqlInput components to
the tELTMysqlMap component using links named
following strictly the actual DB table names: owners,
cars and resellers.
Connect the tELTMysqlMap component to the
tELTMysqlOutput component and name the link
agg_result, which is the name of the database table you
will save the aggregation result to.
Click the tELTMysqlMap component to display its
Basic settings view.
Select Repository from the Property Type list, and select the same DB connection that you use
for the input components.
All the database details are automatically retrieved.
Leave all the other settings as they are.
Double-click the tELTMysqlMap component to launch
the ELT Map editor to set up joins between the input tables and define the output
Add the input tables by clicking the green plus button at the upper left corner of
the ELT Map editor and selecting the relevant table names in the [Add a new alias] dialog box.
Drop the ID_Owner column from the owners
table to the corresponding column of the cars table.
In the cars table, select the Explicit
join check box in front of the ID_Owner column.
As the default join type, INNER JOIN is
displayed on the Join list.
Drop the ID_Reseller column from the
cars table to the corresponding column of the
resellers table to set up the second join, and define the
join as an inner join in the same way.
Select the columns to be aggregated into the output table,
Drop the ID_Owner, Name, and
ID_Insurance columns from the owners
table to the output table.
Drop the Registration, Make, and
Color columns from the cars table to
the output table.
Drop the Name_Reseller and City columns
from the resellers table to the output table.
With the relevant columns selected, the mappings are displayed in yellow and the
joins are displayed in dark violet.
Set up a filter in the output table. Click the Add filter
row button on top of the output table to display the Additional clauses expression field, drop the
City column from the resellers table
to the expression field, and complete a WHERE clause that reads
Click the Generated SQL Select query tab to
display the corresponding SQL statement.
Click OK to save the ELT Map settings.
Double-click the tELTMysqlOutput component to
display its Basic settings view.
Select an action from the Action on data list as
Select Repository as the schema type, and define
the output schema in the same way as you defined the input schemas. In this use
case, select agg_result as the output schema, which is the name
of the database table used to store the mapping result.
You can also use a built-in output schema and retrieve the schema structure from the
preceding component; however, make sure that you specify an existing target table having
the same data structure in your database.
Leave all the other settings as they are.
Save your Job and press F6 to launch it.
All selected data is inserted in the agg_result table as
specified in the SQL statement.