I think most of you already know how to use function lookup(). Unfortunelly I still can't find more details regarding this issue. I need to know how to proper use is and what are the limitations. Right now I'm working on a project where I have 2 tables:
Invoices
Exchange_rates
I need to get the exchange rate to each currency in invoices depending on to which currency I want to transfer the price from Invoices.
function lookup() was created just for that purpose - fetch a single field value from another table based on a certain key value. However, I found Mapping functionality to work better in those cases. For your example, you can create a "RateMap", based on the Currency (and perhaps date?), and then use function ApplyMap(mapname, expression, default) to replace the Currency Code (or Currency-Date) with the corresponding currency rate.
Thanks for your help. But in this case I can't use Maps (I know already how to do it), becouse I need to use exchange rates to convert from one currency to another, dependig what a user wants to do. I used for that combination of functions:
FieldValue() and FieldIndex()
but it's not too good for me (sometimes very slow, many times different results than expected)
I think I should maybe go for profesional traning organized by QlikTech. I need more specific knowledge to better understand how QlikView work.
