Qlik view administrators with the proper admin credentials may now (with qlik view11) generate QVDs directly from the qlik view management console by inserting the QVD generation script as a task in system / supporting tasks/QVD generation. Administrators should enter information in the basics and parameters fields, and click on apply. The task will need to be set up and run to generate the QVD.
The benefit of creating a QVD in this way is avoiding the maintenance of separate QVW files solely to create QVDs.
A QVD file is queried as a data source by qlik view, and the load statement in the qlik view script is all that is necessary to read the QVD data into memory, such as in the following examples.
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Note that QVDs can be read in two modes: optimized (fastest) and standard (fast). The mode is selected automatically via qlik view and is determined by the presence of any data transformations (and formulas or functions acting on the fields). Only on a straight direct read(no transformations) is the optimized mode used. The optimized mode is 10times faster than the standard model (though the standard mode is much faster than reading from a database or flat file).
The following load statement extracts all columns and rows from the sales. Qvd file:
LOAD * from sales. Qvd (qvd);
The next LOAD statement loads only name and ID from the broker.qvd file.
LOAD name, ID from broker.qvd (qvd);
And the final example loads the columns and uses the AS statement to rename those fields (the name is changed to broker-name and ID is changed to broker-ID).
LOAD name as broker-name, ID as
Broker-ID from broker.qvd (qvd);
Since QVDs are proprietary format files, you would typically open and view the values contained in a QVD by opening the QVD in qlik view. You can, however, use notepad or WordPad to view the XML header containing the file attributes of a particular QVD.
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It has become common among qlik view customers to install easy qlik, a third-party QVD viewer tool available at HTTP://WWW.EASYQLIK.COM to view the contents of QVDs (the free version allows you to view thousands of rows, and an upgrade offers more features). Another QVD viewer that is available is Q-eye. It is available at https://www.etl-tools.com.
If you can’t install tools like this on your workstation or server, one of the easiest ways to quickly preview the QVD content is to create a new QVW document and drag a QVD onto the qlik view window. This opens the file wizard: type dialog and allows a limited preview of the columns and rows of data. Clicking on cancel in the wizard closes the QVW and does not create any file.
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If you want to examine all the columns and rows in a QVD, create a quick throw-away qlik view document, load the QVD, and then create a table box with all the data fields in it. Note that if your QVD is very large, you should do a partial reload, restrict via dimension limits, create a condition on the expression, or create calculated limitations for the expressions that would limit the rows that are returned.
A useful tip when dealing with large data sets and QVDs supplying the qlik view application is to open a QVW without data. From the qlik view start page (if it isn’t open, go to the start page window and navigate to help/ show start page), select recently opened documents, then right-click on the desired QVW document. A shortcut menu appears, allowing you to open the document without data; so open the document and reload the data. The shortcut menu also allows you to browse the documents in the folder, add the QVW document to favorites, or remove the QVW document from the recently opened documents list.
The feature that does not display data upon opening is a valuable tool in avoiding time-consuming data loads when opening qlik view applications. if the file is no longer in the recently opened documents list, you can add a/ no data switch to the qlik view program, and this will open your QVW files with no data.
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Note that this feature may get you locked out of any section access in the applications, so test on a copy of the application first
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Vinod Kasipuri writes about various IT platforms such as QlikView, Qlik Sense, and Perl Scripting, at Mindmajix. He loves to explain the concepts he writes in simple terms. He is also engaged in researching trends in AngularJS and LabView. Reach out to him via LinkedIn and Twitter.
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