topic Re: Dealing with null value in variable (inputbox) in QlikView

Dealing with null value in variable (inputbox)

Mon, 26 Jan 2026 18:19:17 GMT

Hi guys

I just think that variable management isn't developed good enough in Qlikview or I just can't get it right (maybe the second affirmation is more probable) .

I get one variable defined in an input box and want to do some calculations with it and null case is a big deal for me, I attached a qvw file to illustrate the situation at a basic level but the expressions I'm using are:

- Left text box: =If($(=len(vVariable))=0, 'Empty', $(vVariable)) => Works good, shows variable value without a problem and 'Empty' when null

- Right text box: =If($(=len(vVariable))=0, 'Empty', 'Value: '&$(vVariable)) => Works good with value, when null I get Expression Error (as you first see)

This is pretty basic but if you replace the else case by another if condition using the vVariable get the same issue.

Do you know how can I correctly handle null value on this case?

Thanks

Re: Dealing with null value in variable (inputbox)

awhitfield — Fri, 20 Feb 2015 16:18:19 GMT

Hi Cristian,

there's no QVW attached to post.

Re: Dealing with null value in variable (inputbox)

Gysbert_Wassenaar — Fri, 20 Feb 2015 16:22:15 GMT

Set a constraint on the input box so the variable cannot be null. Use len($)>0 as Custom Input Constraint.

Or if your variable should contain a number perhaps you can use the alt function: alt($(vVariable), 1234). If vVariable does not contain a number the alt function will return the second parameter as value (1234 in the example).

Re: Dealing with null value in variable (inputbox)

Fri, 20 Feb 2015 16:24:39 GMT

Hi Cristian,

use (isnull) function

Re: Dealing with null value in variable (inputbox)

Fri, 20 Feb 2015 16:51:32 GMT

My bad, thanks for pointing that out. I edited first post to attach the file

Re: Dealing with null value in variable (inputbox)

Fri, 20 Feb 2015 16:56:20 GMT

What I'm really doing is having filters by numbers of ocurrences of a set of hospitalary events and actually need null for exclude some events from my calculation so I can't validate that the input have a value and 0 is a valid value in the calculation.

=If(alt($(vVariable), -1)=-1, 'Empty', $(vVariable)) doesn't work for identify null values, also the problem isn't identifying them (len works just good for that), the problem is that in the else part, I can't use the variable when it has null value. Please see the file attached to my first post

Re: Dealing with null value in variable (inputbox)

Fri, 20 Feb 2015 17:01:26 GMT

It was my first choice but there's a problem: apparently you can't invoke a function in a variable with null value.

I tried with this expression: =If(IsNull($(vVariable)), 'Empty', $(vVariable))

And got: Error: Error in expression:

IsNull takes 1 parameter

My guess is that the behaviour is like the variable doesn't exists at all in case of null value but can't find any function like PHP's isset. I also tried my len approach $(=isNull(vVariable)) without any luck

Please see the file attached to my first post to see the errors I'm having

Re: Dealing with null value in variable (inputbox)

Gysbert_Wassenaar — Fri, 20 Feb 2015 17:17:19 GMT

Don't expand the variable in the expression in the text boxes:

=If($(=len(vVariable))=0, 'Empty', vVariable)

=If($(=len(vVariable))=0, 'Empty', 'Value: ' & vVariable)

Re: Dealing with null value in variable (inputbox)

Fri, 20 Feb 2015 17:24:47 GMT

It works Gysbert thanks but why you don't have to expand the variable? I'm having hard times figuring out when to expand, when no.

My original expression was:

=If($(=len(vFiltroConsultaEspecialista))>0,

If(COUNT({$<CodConsulta={5}, Año={$(=Max(Año))}>} DISTINCT IdActividad)>=vFiltroConsultaEspecialista, COUNT(DISTINCT IdAfiliado_Programa), 'No Value')

)

It works now without expanding in the inner If

Re: Dealing with null value in variable (inputbox)

Fri, 20 Feb 2015 18:00:55 GMT

Try this...

I tried on your qvw and it worked.

find the attachment.

=if(vVariable='','Empty',vVariable)

Re: Dealing with null value in variable (inputbox)

Tue, 24 Feb 2015 16:36:41 GMT

Thanks Rakesh, I still want to know when to expand and when not using expressions in another variables, do you know the common scenarios?

Re: Dealing with null value in variable (inputbox)

Tue, 24 Feb 2015 17:03:54 GMT

did not understand you question?

could you please describe?

Re: Dealing with null value in variable (inputbox)

Tue, 24 Feb 2015 17:14:10 GMT

I mean, when do I have to expand the variable and when no? My expression =If($(=len(vVariable))=0, 'Empty', vVariable) was for another variable in this case. I identify this cases:

1. Using functions: call the function in the expansion of the variable

- len($vVariable) => doesn't work

- len(vVariable) => probably work, haven't tried

- $(=len(vVariable) => Works

2. Conditionals: not expand the variable

- If(condition, $(vVariable), 0) => doesn't work (although it wasn't error)

- If(condition, vVariable, 0) => Works

I wan to better determine these cases or the cases that actually apply

Re: Dealing with null value in variable (inputbox)

Tue, 24 Feb 2015 17:20:18 GMT

ok,

when you'll apply a condition you just need to write variable name no need to apply '$' sign.