topic Re: Variable Evaluation on File Load in QlikView

Variable Evaluation on File Load

Anonymous — Wed, 24 Sep 2014 19:40:34 GMT

I know I've seen this addressed before but I can't find the discussion(s).

When loading variables from a file during script load, how do you keep embedded variables from being evaluated?

For example (off the top of my head, so maybe not a great example):

<Variables.txt>

SET vEndDate = "=Max(Order_Date)";

SET vEndMonth = "=Month($(vEndDate))";

After the variable file is read into the script during load, vEndMonth is doesn't give me 'Sep', for example, it just contains the literal string =Month($(vEndDate).

Re: Variable Evaluation on File Load

Anonymous — Wed, 24 Sep 2014 20:26:25 GMT

you need to write variable "statement" in single quote, instead of double:

SET vEndDate = 'Max(Order_Date)';

Re: Variable Evaluation on File Load

vgutkovsky — Wed, 24 Sep 2014 20:41:08 GMT

You're right, you've seen it before Here's a link to one such discussion with several different solutions: http://community.qlik.com/thread/133348

Vlad

Re: Variable Evaluation on File Load

bimartingo — Fri, 21 Nov 2014 14:10:04 GMT

Hi Brian,

I know, variables evaluation is a very complicated matter, you can never be sure exactly the way they gonna behave, but first of all you have to understand the difference between the SET and the LET instruction.

if you want a variable to evaluate to some value, i. e., using a formula, you'll have to use the LET instruction, not SET.

In your example it would be (with single quotation also corrected)

SET vEndDate = '=Max(Order_Date)';

LET vEndMonth = '=Month($(vEndDate))';

I think it will evaluate to the formula =Month(=Max(Order_Date))

whatever it's meaning is, but I'm not sure.

I'm afraid this is only the beginning of your challenge

Good luck

Re: Variable Evaluation on File Load

Anonymous — Fri, 21 Nov 2014 14:45:50 GMT

Someone at the Qlik conference here in Orlando said that if you are using $ expansion in the variable definition, you do not want to proceed the expression with a = sign since this causes the Ajax client to recalculate the expression on every click, leading to possible performance degradation. Has anyone else heard this?

Re: Variable Evaluation on File Load

Fri, 21 Nov 2014 15:13:53 GMT

Do you mean an equals in the variable itself? If so then yes, the equals will cause it to be a global variable, calculated on each selection. Without the equals you can dollar expand and calculate specifically when you want to

Re: Variable Evaluation on File Load

Anonymous — Fri, 21 Nov 2014 15:30:06 GMT

Thanks for the reply Joe. I'm not sure I follow - can you post an example both ways?

Re: Variable Evaluation on File Load

Fri, 21 Nov 2014 15:35:56 GMT

No problem,

Set vVariable1 = '=Only(Myfieldhere)'

The = results in a global variable

Set vVariable2= 'Only(Myfieldhere)'

without the = does not

Re: Variable Evaluation on File Load

Anonymous — Fri, 21 Nov 2014 15:43:29 GMT

Excellent. What if the variable definition contains a dollar expansion reference to another variable?

Re: Variable Evaluation on File Load

Fri, 21 Nov 2014 15:51:11 GMT

That's fine you are able to do that yes, all the equals is doing in the variable is defining when it is evaluated.

In my example above if you create two text boxes to call each.

Txtbx1:

=vVariable1

would return 'bob' for instance if that was the only selection from Myfieldhere

Txtbx2:

=vVariable2

would return Only(Myfieldhere), as it hasn't been evaluated yet. You would need to do =$(vVariable2) to return 'bob'

hope that makes sense

Joe