Source Qualifier Transformation 

When you add a relational or a flat file source definition to a mapping, you need to connect it to a Source Qualifier transformation. The Source Qualifier transformation represents the rows that the Integration Service reads when it runs a session.

(Read also: Informatica_interview Q&A)

Transformation type:
Active
Connected

Source Qualifier transformation tasks:

	Join data originating from the same source database. You can join two or more tables with primary key-foreign key relationships by linking the sources to one Source Qualifier transformation.
	Filter rows when the Integration Service reads source data. If you include a filter condition, the Integration Service adds a WHERE clause to the default query.
	Specify an outer join rather than the default inner join. If you include a user-defined join, the Integration Service replaces the join information specified by the metadata in the SQL query.
	Specify sorted ports. If you specify a number for sorted ports, the Integration Service adds an ORDER BY clause to the default SQL query.
	Select only distinct values from the source. If you choose Select Distinct, the Integration Service adds a SELECT DISTINCT statement to the default SQL query.
	Create a custom query to issue a special SELECT statement for the Integration Service to read source data. For example, you might use a custom query to perform aggregate calculations. Source Qualifier Transformation Properties Option                                      Description SQL Query : Defines a custom query that replaces the default query.A custom query overrides entries for a custom join or a source filter. User-Defined Join : The condition used to join data from multiple sources represented in the same Source Qualifier transformation. Source Filter : The filter condition the Integration Service applies when querying rows. Number of Sorted Ports : If you select this option, the Integration Service adds an ORDER BY to the default query when it reads source rows. The ORDER BY includes the number of ports specified, starting from the top of the transformation. When selected, the database sort order must match the session sort order. Tracing Level : Amount of detail included in the session log when you run a session containing this transformation. Select Distinct : Specifies if you want to select only unique rows. The Integration Service includes a SELECT DISTINCT statement if you choose this option. Pre-SQL : Pre-session SQL commands to run against the source database before the Integration Service reads the source. Post-SQL : Post-session SQL commands to run against the source database after the Integration Service writes to the target. Output is Deterministic : Relational source or transformation output that does not change between session runs when the input data is consistent between runs. When you configure this property, the Integration Service does not stage source data for recovery if transformations in the pipeline always produce repeatable data. Output is Repeatable : Relational source or transformation output that is in the same order between session runs when the order of the input data is consistent. When output is deterministic and output is repeatable, the Integration Service does not stage source data for recovery.