QV Interview Questions


    A QlikView-application

    Q: How much RAM do I need? Is there a simple way to relate RAM requirements to data volume?
    A: No, it depends on the data structure and the type of data.


    Script and loading data

    Q: Is the only requirement for an automatic join that the field names are the same?

    A: Yes! Such a join is called an association.

    Q: Can I achieve an automatic join between two fields with different field names?

    A: Yes, but you must rename one of the fields in the script using an alias statement or an as clause.

    Q: Can I use where clauses, group by clauses and other SQL-like syntax on binary QlikView files?
    A: No.

    Q: What is the difference between an association between logical tables, a load or select statement preceded by a join qualifier, and a join within a select statement?

    A: An association is a join between logical tables which is evaluated when you click on a field value in your application. QlikView makes this association automatically when two different tables have a field in common. The two latter joins are made during script execution and result in new logical tables. In these cases, QlikView does not load the original tables as logical tables.

    Furthermore, a join within a select statement will usually only load those records whose key field value is found in both tables (inner join), whereas the two former joins also include records whose key field value is found in only one of the tables (full outer join).

    Q: Can I update a QlikView application by loading only the data that have changed?
    A: No. However, new data can be added to your application by combining a binary load with load or select statements.


    QlikView logic

    Q: Why is it impossible to show frequency in certain list boxes?
    A: The list box in which this problem occurs contains a field which is common to more than one input table. It is therefore impossible for QlikView to know how to calculate frequency and other statistical entities for the field. You can solve the problem by reading the field an extra time from its main table (the one you want to have frequency from), but under a new name, and show frequency for that field within the list box instead. By using the label feature, the end user does not have to notice the trick.

    Q: Why does my statistics box come up with just a lot of n/a?

    A: The statistics box contains a field which is common to more than one input table. See the answer to the previous question.

    Q: Why doesn't QlikView allow me to use a certain field in an expression in a chart?
    A: The field is common to more than one input table. See the answer to the two previous questions.

    Q: How can I display the number of distinct values in a statistics box?
    A: Use the distinct clause in your load / select statements.

    Q: When is the AND mode option in the List Box Properties dialog enabled?
    A: The AND mode option is only allowed under very strict conditions, imposed by the theory behind the QlikView logic. In order to be used in AND mode, the field must:

    exist in only one logical table,

    be the second field of only two fields in that table and

    contain no duplicate records.

    Q: Can I mix AND and OR logic for value selections within a list box?
    A: No, the associative logic prohibits this.

    Q: Can I have OR logic between list boxes?
    A: Only indirectly. An advanced alternative is to use semantic links to transfer selections made in a list box to another field. You may then change the selections in the original box and ctrl-click on the semantic link to achieve OR between the two selections. The final result can be transferred by means of reversing the semantic link.

    Q: Is it possible to link more than one info file to a value, e.g. a picture and a text file?
    A: Yes, but only when duplicates of the field are used. Each field in QlikView can only be linked to one info file.

    Q: Why are for instance '002' , '02' and '2' sometimes interpreted as the same value by QlikView?
    A: All the values in the example share the same numeric value. As a rule, QlikView will try a numeric interpretation of any data. If a numeric interpretation is possible, it will be used for the association. If you use the interpretation function text() on a field in the script, however, the values will be treated strictly as text values. The values in the example above will then be interpreted as three different values.

    Q: What is a "loop" or circular table structure?
    A: When it is possible to follow the field associations in a never ending circle through the table structure, this is called a loop. Another way of describing the phenomenon is that there are two or more different routes through the table structure between two specific fields. Loops should be avoided as far as possible since they may cause ambiguities in the way data is interpreted. In many cases loops are a result of poor database design, but in other cases they may be unavoidable. QlikView will issue a warning if it finds a loop while executing the script. Normally QlikView will handle data structures with loops without any problem, but memory demands usually increase as a result.



    Q: Why can't I expand my table to the right when I try to drag the border?
    A: There are two handles on the right border of a table. If you drag the border of a table, you size the outer limits of what can be shown in the table. However, you can never make the outer frame larger than the sum of the widths of all columns in the table. The sizing of the rightmost column is made by putting the cursor just to the left of the outer border. You must however make sure that the outer frame does not fall in the middle of the column. If that is the case, use the scroll bar to position the column's right border at the outer frame.

    Q: Can I change the name of a field in sheet objects in a QlikView document?
    A: Yes, you can set a label for each field in each sheet object.

    Q: Which sheet objects can be minimized?
    A: All types of charts and tables (including table boxes) can be minimized.

    Q: Can I move minimized chart icons on the sheet?
    A: No, the icons are automatically placed at the bottom of the sheet.


    Sharing QlikView applications with other people

    Q: Can I put my application on a server and share it with other people?
    A: Yes, as long as the receivers have a registered QlikView license and access to the server directory.

    Q: Can I put my application as a link on a web-page and let others access it over the net?
    A: Yes, as long as the receivers have a registered QlikView license and access to the web-page.

    Q: Can I e-mail my application to other people?
    A: Yes, as long as the receivers have a registered QlikView license.

    Q: Can I prevent certain people from using my application?
    A: Yes, you can add a "Section Access" to the application to define who may use it.

    Q: Can I prevent other people from seeing/changing the script?
    A: Yes, the "Section Access" can give some people ADMIN access level while keeping other people off the script in USER access level.

    Q: Where do I store information on access rights?
    A: In a text file on a protected unit, as an inline statement in the script or as a table in a database.