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QlikView Interview Questions

Qlikview Interview Questions

Q. Explain Qlikview architecture?

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.


Q. Set analysis in qlikview ?

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


Q. What is  Synthetic key and how to avoid it in QlikView?

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;

Q. Difference between keep and joins ?

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.


Q. Difference between Straight table and pivot table ?

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.


Q. Which graph will you used for two years difference sale ?

BAR Graph


Q. What is Incremental Load in qlikview?

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.


Q. What is Inline memory in QlikView ?

Create table or add field to table .


Q. what is Set and let in QlikView and difference between it?

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″


Q. Explain QlikView Resident Load?

Create a new logical table in QlikView, based on a previously loaded (resident) table.


Q. What is Apply Map (Mapping Tables)?

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 ] )


Q. What is Dimensions ( What is difference between Expression and Dimension)?

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.


Q. Explain about Normalized Data?

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.


Q. What Is Star Sechma ?

A star schema is the simplest form of dimensional model, in which data is organized into facts and dimensions.  A fact is an event that is counted or measured, such as a sale or login.  A dimension contains reference information about the fact, such as date, product, or customer. A star schema is diagramed by surrounding each fact table with its associated dimensions table. The output diagram resembles a star.

Star Schema Definition : A means of aggregating data based on a set of known dimensions. It stores data multidimensionality in a two dimensional Relational Database Management System (RDBMS), such as Oracle.


Q. What is Snowflaking Schema ?

Snowflake Schema: An extension of the star schema by means of applying additional dimensions to the Dimensions of a star schema in a relational environment. Snowflaking is a form of dimensional modeling; dimensions are stored in multiple relational dimension tables.  A snowflake schema is a variation of the star schema. Snowflaking is used to improve the performance of specific queries.  The schema is diagramed with each fact surrounded by its associated dimensions as in a star schema, and those dimensions are further related to other dimensions, branching out into a snowflake pattern.


Q. What is Central Link Table?

In the event of multiple fact tables QlikView In-Memory Technology allows us to create a central link table that only contains the existing data combinations. Instead of Joining the tables the event dimensions can be merged (CONCATENATED) in to one central Link table. This link table can then be linked back to the event measures one side and the dimension tables on the other.


Q. What is binary load ?

Binary load is loading data from another QV file.  For example, you have application A.qvw.  You can create another application B.qvw with script binary A.qvw. binary file  where:

file ::= [ path ] filename

Examples:

Binary customer.qvw;

Binary c:\qv\customer.qvw;

The path is the path to the file, either absolute, or relative to the .qvw file containing this script line.


Q. What is Container ?

A container object can be used to hold multiple charts.  You can use a container object to put multiple charts in the same box. All charts will appear in the same window but only one chart will appear active at a given time. You can click the chart title to switch or toggle between charts. A word of advice: Use containers with caution. They form linked objects and might affect the properties of all linked objects.


Q. What is a synthetic key?

It is a field that contains all possible combinations of common fields among tables.


Q. Define Join and its Types?

Join is used to transform the given data and whenever using joins to transform the data it is called Data Merging. Join will have different types as mentioned below:

Left Join, Right Join, Inner Join and Join


Q. What is Left Join?

The join and keep prefixes in the Qlikview script language can be preceded by the prefix left.

If used before join, it specifies that the join between the two tables should be a left join. The resulting table only contains combinations between the two tables with a full data set from the first table. If used before keep, it specifies that the second table should be reduced to its Common intersection with the first table before being stored in Qlikview.


Q. What is the Right Join?

The join and keep prefixes in the QlikView script language can be preceded by the prefix right. If used before join, it specifies that the join between the two tables with a full data set from the second table. If used before keep, it specifies that the first table should be reduced to its Common intersection with the second table before being stored in QlikView.


Q. What is Inner Join?

The join and keep prefixes in the QlikView script language can be preceded by the prefix inner. If used before join, it specifies that the join between the two tables should be an innder join. The resulting table contains only combinations between the two tables with a full data set from both sides. If used before keep, it specifies that the two tables should be reduced to their common intersection before being stored in QlikView.


Q. How does Join Works?

An operation that uses two tables and combines them into one. The records of the table produced are combinations of records in the two original tables, usually such that the two records contributing to any given combination in the produced table have a common value for one or several common fields, a so called natural join. In QlikView, joins can be made in the script, producing logical tables. Inner join, Left join, Right join and Outer join are all possible operations.

Mindmajix qlikview Expert trainers discuss the interview questions at the end of the Qlikview Training.


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