Sql mapping help

Hi guys,

I have just started my 1st mapping exercise and confused.. Really need all of your help. Please help it's urgent.

I have 2 sources.. Source A is passing variable A and source B is passing Variable B.
The transformation logic is
Variable A=word(Variable B)
If variable A= 7 then
Boolean exp = 1
Else boolean exp= 0

Then the output of this transformation logic is the booloean expression.

I have data mapping table which needs source name, source table name, source field name, key, translation logic, output variable. Please vlarify how this example would fit in the table.. Appreciate your help thanks.