topic Re: Strange behaviour with for loop and peek? in QlikView

Strange behaviour with for loop and peek?

chrisbrain — Wed, 13 Jul 2011 08:26:47 GMT

This is confusing me! I have a table which I can correctly peek at values in using the following:

let y = peek('page', 0, FacebookProConnector_Page); // y = "value1'

let y = peek('page', 1, FacebookProConnector_Page); // y = "value2'

let y = peek('page', 2, FacebookProConnector_Page); // y = "value3'

However, in a for loop, e.g.:

let noRows = NoOfRows('Table1');

for i=0 to $(noRows) // loop through every row

let y = peek('page', $(i), Table1);

// Additional load statement to other table here

I get weird behaviour.

- in the first iteration (i=0), y is correctly 'value1'

- In the second iteration (i=1), y = NULL ?????

But this only happens if I have the additional load statement (where the comment is above) present. If I remove the inner load to another table (and just have an empty loop) it seems to work ok.

I can't see what I could be doing wrong - would appreciate any ideas.

This is happening QlikView 9 desktop.

Strange behaviour with for loop and peek?

martin59 — Wed, 13 Jul 2011 08:41:03 GMT

Hi,

What is you Additional load statement ?

Strange behaviour with for loop and peek?

chrisbrain — Wed, 13 Jul 2011 08:49:46 GMT

Structurally it is along the lines of this.

for i=0 to $(noRows) // loop through every row

let y = peek('page', $(i), Table1);

let x = peek('page_id', $(i), Table1);

Table2:

LOAD

$(x) as field_id,

field1,

field2,

etc.

FROM

[http://localhost:5555/QVSource/Connector/?config=$(y)]

(txt, utf8, embedded labels, delimiter is '\t', msq);

Strange behaviour with for loop and peek?

martin59 — Wed, 13 Jul 2011 09:10:58 GMT

I see anything wrong.

Have you a value for i=2, i=3 or always NULL ?

Is your X variable is in numeric format ?

Strange behaviour with for loop and peek?

Wed, 13 Jul 2011 11:25:35 GMT

Hi Chris,

When I added quotes around the 'table name' it seemed to work, so:

let y = peek('page', 0, 'FacebookProConnector_Page');

instead of

let y = peek('page', 0, FacebookProConnector_Page);

Strange behaviour with for loop and peek?

chrisbrain — Wed, 13 Jul 2011 11:58:15 GMT

Thanks rsmeding! - That fixed it!

The QlikView docs/help file seems to suggest you don't need/use the apostrophes but it seems you do.

Re: Strange behaviour with for loop and peek?

rwunderlich — Wed, 13 Jul 2011 22:45:55 GMT

Hi Chris,

This is a common error and a difficult to debug issue. There used to be an article in the old wiki about it but that wiki is now gone.

What happens is this. Without the quotes, the tablename is not correcly resolved and so defaults to the current table. When you add the load statement, you change the current table to a table that did not contain field "page".

-Rob

//http://robwunderlich.com

Re: Strange behaviour with for loop and peek?

chrisbrain — Thu, 14 Jul 2011 14:01:48 GMT

Hi Rob,

Thanks for the additional info - good to know it wasn't just me..

Re: Strange behaviour with for loop and peek?

rbecher — Thu, 14 Jul 2011 19:40:56 GMT

Hi all,

they should change or mention this in the doc. There are several issues in the doc we've pointed out earlier. Maybe we can collect those things in the QlikBug group.

- Ralf

Re: Strange behaviour with for loop and peek?

rwunderlich — Thu, 14 Jul 2011 20:23:00 GMT

I started to write a bug report and then realized this is not a bug, although it could probably use some clarification. It's legal to use a fieldname to reference the tablename, in which case you would not quote. For example:

data1:

LOAD * INLINE [

];

data2:

NOCONCATENATE LOAD * INLINE [

];

control:

LOAD * INLINE [

Table

data1

data2

];

new:

LOAD

Table,

peek('V1', 0, Table) as PeekVal

RESIDENT control;

Re: Strange behaviour with for loop and peek?

rbecher — Thu, 14 Jul 2011 20:36:13 GMT

Hi Rob,

interesting approach! But, that means Tablename is a string and not a "table label without the ending colon" as doc says.

- Ralf