Database Reference
In-Depth Information
Source Qualifier transformation
Source Qualifier transformation act as virtual sources in Informatica. When you drag a re-
lational table or flat file in Mapping Designer, the Source Qualifier transformation comes
along with it. A source qualifier is the point where the Informatica processing actually
starts. The extraction process starts from the source qualifier.
Note that it is always recommended that the columns of source and source qualifier match.
Do not change the columns or their data type in the source qualifier. You can note the data
type difference in the source definition and source qualifier, which is because Informatica
interprets the data in that way itself.
To discuss the source qualifier, let's take an example of the Joiner transformation mapping
we created earlier.
As you can see, there are two Source Qualifier transformations present in the mapping: one
for flat file and the other for a relational database. You can see that we have connected only
three columns from the Source Qualifier transformation of flat file to the Joiner transforma-
tion. To reiterate the point, all the columns are dragged from the source to source qualifier,
and only three columns are linked to the Joiner transformation. This indicates that the
source qualifier will only extract data that's related to three ports, not all. This helps in im-
proving performance, as we are not extracting the unwanted columns' data.
In the same mapping, another Source Qualifier transformation is connected to a relational
source. Multiple options are possible in this case. We will discuss each option in detail in
the upcoming sections.
