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SSIS Interview Questions and Answers

Difference between control flow and data flow

Control flow deals with orderly processing of individual, isolated tasks, these tasks are linked through precedence constraints in random order. Also the output for task has finite outcome i.e., Success, Failure, or Completion. A subsequent task does not initiate unless its predecessor has completed. Data flow, on the other hand, streams the data in pipeline manner from its source to a destination and modifying it in between by applying transformations. Another distinction between them is the absence of a mechanism that would allow direct transfer of data between individual control flow tasks. On the other hand, data flow lacks nesting capabilities provided by containers.

What is SSIS?

SSIS was first introduced with SQL Server 2005, which was the next generation of SQL Server software after SQL Server 2000. SSIS is a form of ETL (extraction, transformation and load), which is a database term that integrates data scheduling and tasks. The SSIS engine automation many data maintenance tasks, so you can update data without manually firing procedures and imports.

Error Handling in SSIS?

An error handler allows us to create flows to handle errors in the package in quite an easy way. Through event handler tab, we can name the event on which we want to handle errors and the task that needs to be performed when such an error arises. We can also add sending mail functionality in event of any error through SMTP Task in Event handler. This is quite useful in event of any failure in office non-working hours. In Data flow, we can handle errors for each connection through following failure path or red arrow.

What kind of variables can you create?

You can create global variables and task level variables in SSIS. For programmers, these variables are the same as global and function level variables. A global variable is available to all tasks across the entire job. Variables created in tasks are only available within that task.

If you want to send some data from Access database to SQL server database. What are different component of SSIS will you use?

In the data flow, we will use one OLE DB source, data conversion transformation and one OLE DB destination or SQL server destination. OLE DB source is data source is useful for reading data from Oracle, SQL Server and Access databases. Data Conversion transformation would be needed to remove datatype abnormality since there is difference in datatype between the two databases (Access and SQL Server) mentioned. If our database server is stored on and package is run from same machine, we can use SQL Server destination otherwise we need to use OLE DB destination. The SQL Server destination is the destination that optimizes the SQL Server.

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