topic Re: how to avoid nested if in QlikView

how to avoid nested if

Wed, 26 Feb 2014 16:00:18 GMT

I have an expression that is essentially:

if exp1 is not null then

exp1

else

exp2;

if exp2 is not null then

exp2

else

exp3;

etc...

if expn is not null then

expn

else

'Unknown';

I can't do this in the load statement because each of these expressions are based off of user input. Essentially, I have a hierarchy classifications. A record could have a value for several different sources of classifications and the user can change their hierarchy (preferred order of classifications) for all securities. Some securities may only have classifications from a classification source that the user does not select, which is the reason for the 'Unknown' at the end of the nested if. I'm hoping there is a better way to do this process in QV as it will be pervasive across many reports and I expect would hit performance. Any suggestions would be greatly appreciated.

Re: how to avoid nested if

marcus_sommer — Wed, 26 Feb 2014 16:09:54 GMT

You could try it with the function alt().

- Marcus

Re: how to avoid nested if

ThornOfCrowns — Wed, 26 Feb 2014 16:11:11 GMT

This: http://community.qlik.com/docs/DOC-5841 might help, hopefully.

Re: how to avoid nested if

Wed, 26 Feb 2014 16:15:22 GMT

That link says at the end that the speed compared to a nested if was not any different. Is my assumption that nested ifs are big hits to performance?

Re: how to avoid nested if

marcus_sommer — Wed, 26 Feb 2014 16:23:16 GMT

If-Statements are always slow. But you could try it with conditions on the expressions - this means you have no nested if then only the expression(s) with a valid condition will be displayed.

- Marcus

Re: how to avoid nested if

Clever_Anjos — Wed, 26 Feb 2014 16:25:13 GMT

alt(exp1,exp2,exp3,exp4,'Unknow')

Re: how to avoid nested if

Wed, 26 Feb 2014 16:30:49 GMT

does alt only work on numbers?

Re: how to avoid nested if

Clever_Anjos — Wed, 26 Feb 2014 16:33:55 GMT

Yes

Re: how to avoid nested if

Wed, 26 Feb 2014 16:35:53 GMT

Is alt significantly faster than a nested if? I can probably convert the field i'm working with to duals, allowing alt to work on them but return the strings I need.

Re: how to avoid nested if

Clever_Anjos — Wed, 26 Feb 2014 16:45:37 GMT

I´ve never tested speed of both.

I generally use it because is much 'cleaner' to read and mantain