how to add an intermediate calculated "variable" in informatica

I am an Informatica newbie, and making a flow like:

(Source A - Source A Qualifier) and (Source B - Source B Qualifier) -> Joiner -> Target

say I need to calculate a a variable/column over Source A in order to join Source A and Source B.

Can you please help me how to d开发者_开发技巧o that?

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You can use an Expression transformation to calculate the value required. This would be placed between Source A and the joiner, with an output only port added with the logic inside.

However, if the calculation is simple enough, you can have it pre-computed in the SQL query for Source A. This is advantageous as it will allow you to sort both sources on the common column(s) and use the Sorted Input option on the Joiner, which performs much better.