Qlikview Interview Questions & Answers (Part-1)

1. Explain architecture of Qlikview?
 
A: QlikView deployments have three main infrastructure components:

1.QlikView Developer :  Is a Windows-based desktop tool that is used by designers and developers to create

1) a data extract and transformation model and
2) to create the  graphical user interface (or presentation layer).

2.QlikView Server (QVS) : Handles the communication between clients and the QlikView applications. It loads QlikView applications into memory and calculates and presents user selections in real time.

3.QlikView Publisher: Loads data from different data sources (oledb/odbc, xml, xls), reduces the QlikView application and distributes to a QVS.

Because QlikView Server and Publisher have different roles and handle CPU and memory differently it’s considered a best practice to separate these two components on different servers.

  2. What is  Synthetic key in Qlikview and how to avoid it?

A: It is undesirable to have multiple common keys across multiple tables in a QlikView data structure. This may cause QlikView to use complex keys (a.k.a. synthetic keys) to generate the connections in the data structure. Synthetic keys are generally resource heavy and may slow down calculations and, in extreme cases, overload anapplication. They also make a document harder to understand and maintain. Thereare some cases where synthetic keys cannot be avoided (e.g. Interval Match tables),but, in general, synthetic keys should always be eliminated, if possible.

1. comment the fileds in load script
2. rename the fileds in load script
3. rename the fileds using UNQUALIFY operator;

3.  how Set analysis defined in qlikview  ?

A: Used for set of groups. mostly used in arrgeted function like sum (year) used    sales of current year VS last year.

 4. What is Difference between Straight table and pivot table ?
 
A :  Pivot Table -

1) A pivot table is better at grouping: you can easily see which group a specific row belongs to, and a group can have a subtotal.

2) You can also display a pivot table like a cross table (one or several horizontal dimensions).

3) But when you sort a pivot table, you have to sort it first according to the first dimension, then according to the next, etc.
You cannot sort it any way you want.
Straight Table-

A straight table is better at sorting than a pivot table: you can sort it according to any column.
But it is not so good at grouping. Subtotals are not possible, for instance.

5   Difference between keep and joins in Qlikview ?

A: Left Keep and Left join gives the same output. The only difference is that Left Keep keeps the Table separate in Data Model, whereas Left join merges the Tables that are joined.

6.  What is Incremental Load ?

A :  As BI apps are expected to deal with larger and larger amounts of data the amount of time that it takes to retrieve that data becomes a serious issue.  This could be due to shear volume of data or the need for frequent refreshes. Either way, you do not want to be pulling all of the data all of the time. What you want to be able to do is just pull the data that has changed, append to that the data that you stored away previously and then get back to the business of analyzing.  This will reduce load on the source database, the network infrastructure and your QlikView server.

7. what is Set and let and difference between it?

A:    SET or a LET statement is often usedTo define the variable. The SET statement is used when you want a variableto hold the string or numeric value that is to the right of the Equal (=) sign.

The LET statement is used when you need to evaluate what is to the right of the Equal sign

e.g : set myVar=5*2   the result is “5*2″
         Let myVar=5*2   the result is “10″

8.  What are Mapping Tables ?

A:  Sometimes you need to add an extra field to a table to use a combination of fields

from different tables, or you want to add a field to clean up the data structure. Qlik- View has an effective way to add single fields to a table called mapping tables.  syntax — mapping ( load statement | select statement )
applymap( ‘mapname’, expr, [ , defaultexpr ] )

9. Difference between Expression and Dimension ?

  A:  Each data warehouse consists of dimensions and measures. Dimensions allow data analysis from various perspectives. For example, time dimension could show you the breakdown of sales by year, quarter, month, day and hour. Product dimension could help you see which products bring in the most revenue. Supplier dimension could help you choose those business partners who always deliver their goods on time. Customer dimension could help you pick the strategic set of consumers to whom you’d like to extend your very special offers.

10. Explain about Normalized Data ?

 A:  Well Structured Form of Data, which doesnt have any repetition or redundancy of data. Its a kind of Relational data. Its mainly used in OLTP kind of stuffs Denormalized Data – Its a whole bunch of data without any relationship among themselves, with redundancy of data. Its mainly used in OLAP kind of stuffs.