update dynamic lookup value

Question

how can I update a value in a dynamic lookup in the follow manner:

say I have an integer column in the lookup and on the next lookup I get a new integer that should be added to the existing value.

how can i achieve it?

for example:

I have the empty source table

emp_id | value

row insert                        emp_id | value
1) 101, 1000  expecting insert      101    1000
2) 101, 1005  expecting update      101    2005    
3) 101, -300  expecting update      101    1705

I hope my example is clear

Answer 1

There is an option within the "Properties" tab of the lookup transformation that will give you what you need.

However, if set this can cause performance degradation within the mapping and is something I generally try and avoid setting. I am usually able to avoid setting this parameter by including more logic in the Source Qualifier SQL override, e.g. in your example to ensure I only return the most recent record for each employee.