Free Talend Data-Integration-Developer Practice Exam with Questions & Answers | Set: 2

The Use or register a shared DB Connection option in Talend Studio is an option that allows you to share a single database connection between multiple components in a job or between parent and child jobs. This option can improve the performance and efficiency of your job by avoiding opening and closing multiple connections to the same database. The Use or register a shared DB Connection option is compatible with the following scenarios:

• Sharing a connection between parent and child jobs. You can use this option to pass a database connection from a parent job to a child job that is called by a tRunJob component. This way, you do not need to create a new connection in the child job, but reuse the existing one from the parent job.
• Sharing a connection between components in the same subjob. You can use this option to register a database connection in one component (such as tMysqlConnection) and use it in other components (such as tMysqlInput or tMysqlOutput) in the same subjob. This way, you do not need to configure each component with the same connection properties, but use a shared one.

The Use or register a shared DB Connection option is incompatible with the following scenarios:

• Using an independent process to run subjob option of tRunJob component. This option allows you to run a child job in a separate JVM process from the parent job. This option is not compatible with sharing a database connection, because each JVM process has its own memory space and cannot access the objects of another process.
• Using dynamic job option of tRunJob component. This option allows you to call a child job dynamically based on a context variable that contains the name of the child job. This option is not compatible with sharing a database connection, because dynamic jobs are loaded at runtime and cannot access the metadata of other jobs. References: Talend Open Studio: Open-source ETL and Free Data Integration | Talend, [Use or register a shared DB Connection - 7.3], [tRunJob properties - 7.3]

To trigger auto-completion in Talend Studio, you can use the keystrokes Ctrl + Space. This will display a list of possible suggestions based on what you have typed so far. For example, if you type context. and press Ctrl + Space, you will see a list of all the context variables you have defined. You can then select the one you want from the list or continue typing to narrow down the choices. Auto-completion can help you avoid typing errors and save time when configuring components or writing expressions. References: Talend Open Studio: Open-source ETL and Free Data Integration | Talend

The tMap component allows you to set up a filter on the input fields by using the Expression filter in the output table. The Expression filter is a field where you can enter a logical expression that evaluates to true or false for each input row. For example, if you want to filter out the rows that have null values in a certain column, you can use row1.column != null as the expression filter for that output. The expression filter applies to all the input fields of the row, not just a single column. You cannot set up a filter on the input fields by using the Match Model parameter field for one of the inputs or outputs, as this field is used to define how to match rows between different inputs or outputs based on a key attribute. References: Talend Open Studio: Open-source ETL and Free Data Integration | Talend

The tMap component allows you to configure multiple outputs for your data transformation and mapping. You can apply filter expressions on each output to filter out the rows that meet certain criteria. For example, if you want to send only the rows that have CA as the state value to one output, you can use CA.equals(row1.state) as the filter expression for that output. The filter expression evaluates to true or false for each row, and only the rows that evaluate to true are sent to the output. In this case, only Thomas Coolidge and Andrew Taylor have CA as their state value, so they are sent to the CA output. Similarly, only Calvin Adams has NY as his state value, so he is sent to the NY output. The Rejects output has no filter expression, so it receives all the rows from the input by default. However, since there is a conflict between the CA and NY outputs and the Rejects output, only the rows that are not sent to any other output are sent to the Rejects output. In this case, there are no such rows, so the Rejects output receives no data. References: Talend Open Studio: Open-source ETL and Free Data Integration | Talend,

To reference the value of a context variable you defined, you can use the syntax context.variable_name, where variable_name is the name of the context variable. For example, if you have a context variable named path, you can reference its value by using context.path. You do not need to specify the context name (such as test or prod) or use parentheses or brackets around the variable name. References: Talend Data Integration — Software to Connect, Access, and Transform Data | Talend,

To create a centralized metadata connection to a database server for an application, you need to take the following steps before building a job that reads from that database:

• Create DB Connections metadata to describe the database connection. You can do this by right-clicking on the DB Connections node in the Repository and selecting Create Connection. You can then enter the connection details, such as host, port, database, username, password, etc., and test the connection.
• Retrieve schemas from the database connection. You can do this by expanding the DB Connections node in the Repository and right-clicking on the connection you created. You can then select Retrieve Schema and choose the tables or views you want to import as metadata schemas. You can also edit or customize the schemas as needed.
• Drag the DB Connection metadata into the Designer to read from the database component. You can do this by dragging the connection or a specific schema from the Repository to the Designer workspace. This will automatically create a database input component (such as tMysqlInput) that is configured with the connection and schema properties. You can then use this component to read data from the database in your job.

You do not need to add a tMap component to handle and convert DB Types, nor a tCreateTable component to create a table in the database. These components are not required for reading data from an existing database, but they can be used for other purposes, such as transforming or writing data. References: Talend Open Studio: Open-source ETL and Free Data Integration | Talend, [DB Connections - 7.3], [tMap properties - 7.3], [tCreateTable properties - 7.3]