QlikView "field not found" workaround for adding a new field - field

Question

I am trying to get my script to reload in QlikView without success. I have added a new field (named Litres) to my most recently generated QVD files. However, my older QVD files do not have this Litres field which therefore causes the script to error out with the "Field not found" error.
I am trying to do the following:
Search for all the fields in the QVD
If the Litres field exists, then load the data into QlikView.
If not, create the field with a value of zero and continue.
The above should not result in an error.
My current script is below:
/* get all sales csvs */
sales:
load 2014 as Year
AutoGenerate 0;
set FilePath = ..\..\SourceData\qv-sales*.csv;
for each File in filelist('$(FilePath)')
/* load qvd file if it is newer than csv file */
temptable1:
first 1 LOAD
*
FROM $(File)
(txt, codepage is 1252, embedded labels, delimiter is ',', msq);
IF FieldNumber('Litres' , 'temptable1') <> null then
SET "Litres";
SET "Litres LY" ;
SET dyncode2 = P-Value;
SET dyncode3 = O-P-Value;
SET dyncode4 = P-Value LY;
SET dyncode5 = O-P-Value LY;
SET dyncode6 = P-Qty;
SET dyncode7 = P-O-Qty;
SET dyncode8 = P-Qty LY;
SET dyncode9 = P-O-Qty LY;
ENDIF;
DROP TABLE temptable1;
let qvdFile = replace('$(File)','csv','qvd');
if (QvdCreateTime('$(qvdFile)') >= FileTime('$(File)')) then
/* load qvd file if it is newer than csv file */
sales:
Concatenate (sales) load
"GP",
"O-GP",
"Litres",
"Litres LY",
"GP LY",
"O-GP LY",
$(dyncode2) as "P-Value",
$(dyncode3) as "O-P-Value",
$(dyncode4) as "P-Value LY",
$(dyncode5) as "O-P-Value LY",
$(dyncode6) as "P-Qty",
$(dyncode7) as "P-O-Qty",
$(dyncode8) as "P-Qty LY",
$(dyncode9) as "P-O-Qty LY" from $(qvdFile) (qvd);
else
/* create temp store key1 & key2 are manually handled synthetic keys */
/* Dummy field is to prevent autoconcatenation problems. */
temptable:
noconcatenate Load
"GP",
"O-GP",
"Litres" ,
"Litres LY",
"GP LY",
"O-GP LY",
$(dyncode2) as "P-Value",
$(dyncode3) as "O-P-Value",
$(dyncode4) as "P-Value LY",
$(dyncode5) as "O-P-Value LY",
$(dyncode6) as "P-Qty",
$(dyncode7) as "P-O-Qty",
$(dyncode8) as "P-Qty LY",
$(dyncode9) as "P-O-Qty LY",
autonumber(1) as dummy1
FROM $(File) (ansi, txt, delimiter is ',', embedded labels);
/* create qvd file from temp table */
if (ScriptErrorCount = 0) then
Store temptable into $(qvdFile);
endif
sales:
concatenate("sales") load
"Litres",
"Litres LY",
"GP LY",
"O-GP LY"
"P-Value",
"O-P-Value",
"P-Value LY",
"O-P-Value LY",
"P-Qty",
"P-O-Qty",
"P-Qty LY",
"P-O-Qty LY"
resident temptable;
/* drop temp table */
DROP TABLE temptable;
endif
next File
Thanks in advance!

Answer 1

You can use the FieldNumber function to determine whether a field exists in a table. For example FieldNumber('MyField', 'MyTable') returns the position of MyField within MyTable. If MyField does not exist in MyTable the function returns zero.
You can adapt this to your advantage by loading all fields from your QVD into a temporary table and then checking to see if this table contains the field. If it does, you can continue loading. If not, you can simply set the field to zero.
I have adapted your script and inserted an IF for this purpose:
/* get all sales csvs */
sales:
load 2014 as Year
AutoGenerate 0;
set FilePath = ..\..\SourceData\qv-sales*.csv;
for each File in filelist('$(FilePath)')
/* load qvd file if it is newer than csv file */
temptable1:
first 1 LOAD
*
FROM $(File)
(txt, codepage is 1252, embedded labels, delimiter is ',', msq);
IF FieldNumber('Litres' , 'temptable1') <> null then
SET "Litres";
SET "Litres LY" ;
SET dyncode2 = P-Value;
SET dyncode3 = O-P-Value;
SET dyncode4 = P-Value LY;
SET dyncode5 = O-P-Value LY;
SET dyncode6 = P-Qty;
SET dyncode7 = P-O-Qty;
SET dyncode8 = P-Qty LY;
SET dyncode9 = P-O-Qty LY;
ENDIF
DROP TABLE temptable1;
let qvdFile = replace('$(File)','csv','qvd');
if (QvdCreateTime('$(qvdFile)') >= FileTime('$(File)')) then
/* load qvd file if it is newer than csv file */
fieldcheck:
FIRST 1
NOCONCATENATE
LOAD
*
FROM $(qvdFile) (qvd);
if FieldNumber('Litres','fieldcheck') = 0 then
drop table fieldcheck;
sales:
Concatenate (sales) load
"GP",
"O-GP",
0 as "Litres",
0 as "Litres LY",
"GP LY",
"O-GP LY",
$(dyncode2) as "P-Value",
$(dyncode3) as "O-P-Value",
$(dyncode4) as "P-Value LY",
$(dyncode5) as "O-P-Value LY",
$(dyncode6) as "P-Qty",
$(dyncode7) as "P-O-Qty",
$(dyncode8) as "P-Qty LY",
$(dyncode9) as "P-O-Qty LY" from $(qvdFile) (qvd);
else
drop table fieldcheck;
sales:
Concatenate (sales) load
"GP",
"O-GP",
"Litres",
"Litres LY",
"GP LY",
"O-GP LY",
$(dyncode2) as "P-Value",
$(dyncode3) as "O-P-Value",
$(dyncode4) as "P-Value LY",
$(dyncode5) as "O-P-Value LY",
$(dyncode6) as "P-Qty",
$(dyncode7) as "P-O-Qty",
$(dyncode8) as "P-Qty LY",
$(dyncode9) as "P-O-Qty LY" from $(qvdFile) (qvd);
endif
else
/* create temp store key1 & key2 are manually handled synthetic keys */
/* Dummy field is to prevent autoconcatenation problems. */
temptable:
noconcatenate Load
"GP",
"O-GP",
"Litres" ,
"Litres LY",
"GP LY",
"O-GP LY",
$(dyncode2) as "P-Value",
$(dyncode3) as "O-P-Value",
$(dyncode4) as "P-Value LY",
$(dyncode5) as "O-P-Value LY",
$(dyncode6) as "P-Qty",
$(dyncode7) as "P-O-Qty",
$(dyncode8) as "P-Qty LY",
$(dyncode9) as "P-O-Qty LY",
autonumber(1) as dummy1
FROM $(File) (ansi, txt, delimiter is ',', embedded labels);
/* create qvd file from temp table */
if (ScriptErrorCount = 0) then
Store temptable into $(qvdFile);
endif
sales:
concatenate("sales") load
"Litres",
"Litres LY",
"GP LY",
"O-GP LY"
"P-Value",
"O-P-Value",
"P-Value LY",
"O-P-Value LY",
"P-Qty",
"P-O-Qty",
"P-Qty LY",
"P-O-Qty LY"
resident temptable;
/* drop temp table */
DROP TABLE temptable;
endif
next File

Answer 2

If my understanding is correct you need to regenerate your QVDs because you added a new field which doesn't exists in the previous ones, so you recreate them from the source (txt) and store them.
A simpler way to achieve this is to take advantage of the fact that when you do a forced concatenate with a table the missing fields will be generated with null, which we can use with the function alt to transform the null into 0.
so taking your example:
/* get all sales csvs */
sales:
load 2014 as Year
AutoGenerate 0;
set FilePath = ..\..\SourceData\qv-sales*.csv;
for each File in filelist('$(FilePath)')
let qvdFile = replace('$(File)','csv','qvd');
//this generate the field Litres, exists or not
tmp: noconcatenate load null() as Litres autogenerate(0);
if (QvdCreateTime('$(qvdFile)') >= FileTime('$(File)')) then
/* load qvd file if it is newer than csv file */
concatenate(tmp) LOAD * FROM $(qvdFile) (qvd);
else
concatenate(tmp) LOAD * FROM $(File)
(txt, codepage is 1252, embedded labels, delimiter is ',', msq);
endif;
tmp_sales:
noconcatenate
load
alt(Litres,0) as Litres,
"Litres LY",
"GP LY",
"O-GP LY"
"P-Value",
"O-P-Value",
"P-Value LY",
"O-P-Value LY",
"P-Qty",
"P-O-Qty",
"P-Qty LY",
"P-O-Qty LY"
resident tmp;
drop table tmp;
//if it was newer that the csv we store it
if (QvdCreateTime('$(qvdFile)') >= FileTime('$(File)')) then
Store tmp_sales into $(qvdFile);
endif
concatenate(sales) load * resident tmp_sales;
drop table tmp_sales;
next File