What is Keep?

Keep: it will not join two tables and they will be stored in QlikView as two separate named tables. Keep will always preceded by one of the prefix

• Inner
• Left
• Right 

Ex. Right Keep.

What is the difference between Subset ratio & Information Density?

Information density of the field, which indicates the percentage of rows that contain a non-null value 

Subset ratio, which shows the percentage of all distinct values for a field in the table compared to all the distinct values for that field in the entire data model. It is only relevant for key fields since they are present in multiple tables and do not all share the same value. 

Subset ratios can be used to easily spot problems in key field associations. 

For example, when the combined total of subset ratios for multiple tables is 100 percent, this may indicate that there are no matching keys between these tables.

How do you optimize QlikView Application?

For Optimization we can optimized the QVD which is used in the QVW files in the backend. For QVW optimization I believe not use any tools we can manually remove unwanted fields form data model or comment it, remove most complex logics from the load script or create it with the simple way because it will take long time for loading. If using large data base file try to create the incremental load for the QVD or load latest data only.

How are NULLS implemented in QlikView?

The way in which QlikView's associative engine works means Nulls don't really exist in the data it holds, a Null is simply an absence of a data item. For example if a field value is missing we can’t make selection on empty list box. We can replace these null values with our required values (NA, 0, etc…)

What are the restrictions of Binary Load?

Binary load is used only for one application means you are able to read data from only one QVW application and on the above of the set scripts is a restriction. In QlikView data is stored in QVDs but if you are using any QVW application data is loaded in the RAM that’s why it is called as In-Memory analysis tool.

Briefly explain how does QlikView storage the data internally?

QlikView store data in to QVD. QVD have data compression capability. QlikView have better performance compared to other BI because of in memory analytics approach, in built ETL handling capability.

Explain 3 tier architecture implementation while deploying QlikView application?

1st Tier - Raw data is getting loaded and QVD is creating.

2nd Tier - QVD is transform in the business login and requirement of the business and data model is created.

3rd Tier - Reading the all QVD from 2nd tier and make a single QVW or may be any binary load.

Optimized and UN optimized QVD Load Situations?

Optimized load is much faster and therefore preferable, especially for larger data sets. Optimized loads are possible if no transformations (calculations) are made during the load, and no (almost) filtering is done in a WHERE clause.

The only acceptable filter is using function Exists: 
WHERE Exists (Field) 
So for example this load can't be optimized: 
Load * From ... WHERE Country = 'US' 
But this load can: 
Load * From ... WHERE EXISTS (Country) 

On the other hand, the only time you want the load not to be optimized, is if you load a Mapping table from a QVD file. In this case, Optimized load doesn't quite work, so you want to make the load non-optimized deliberately.

What is Mapping Load & Apply Map ()?

Mapping Load: The mapping prefix is used on a load or select statement to create a mapping table, these tables are different from other tables. They will be stored in separate area of memory and used as mapping tables during script execution. After execution they will automatically drop.

Ex. Mapping (Load Statement/Select Statement) 

Apply Map: used for mapping data from one source to another at load time. 

Ex. Apply map(Map name, expr,[default expr])

What is the difference between ODBC, OLE DB & JDBC?

The differences between these two data access protocols are technical, but in the most general terms, OLE DB is newer, more advanced, and compatible with a wider selection of database technologies. In addition, OLE DB is more general, in that it includes the ODBC functionality. 
Technically speaking, ODBC (Open Database Connectivity) is designed to provide access primarily to SQL data in a multi-platform environment. OLE DB (Object Linking and Embedding Database) is designed to provide access to all types of data in an OLE Component Object Model (COM) environment. OLE DB includes the SQL functionality defined in ODBC but also defines interfaces suitable for gaining access to data other than SQL data.
A query generated via ODBC is functionally similar to a query generated by OLE DB. However, be aware that if you generate a query (via STATISTICA Query) using an ODBC connection, STATISTICA uses OLE DB to connect to the ODBC connection. Because there is an intermediate connection, ODBC queries may be slower than OLE DB queries.

Interview Questions on QlikView Scripting

What is the use of Cross table prefix in QlikView Load Script?
What is the difference between Map Using and Mapping Load?
Synthetic Keys in QlikView and how & when to avoid them?
Different flavors’ of Joins in QlikView?
What is the difference between Join & Keep?
How do you use having clause (SQL Equivalent) along with Group by in QlikView?
Explain Interval Match function in QlikView?
Explain Concatenation, No Concatenation & Auto Concatenation?
Explain how to implement Incremental Load?
What is Circular Loop and how do you avoid it?
Explain Exists () function in QlikView and when do you use this function?
What is Generic Load in QlikView?

QlikView Interview Questions on QlikView Security

Describe Section Access architecture?
What is the difference between Authentication & Authorization in QlikView? And how to implement them?
What is the difference between File System Security vs Section Access?
Explain “Strict Exclusion” while implementing Section Access and what are the implications of not using this option?
How do you implement Section Access on hierarchy based data?

QlikView Server & Publisher Interview Questions

What are the multiple protocols defined for client communication with QVS?
Explain different communication encryptions for Windows Client & AJAX Client?
What is the use of Anonymous User Account in QVS?
What are the different types of CALs and explain them?
What are the different editions of QlikView Server?

QlikView Expression Language/UI Interview Questions

Explain Aggr Function? 

What is the use of First Sort Value in QlikView? 

What are Set Modifiers and Set Identifiers? 

What is P() & E() and where do you use them? 

What is the difference between Value List() and Value Loop()? 

What is Partial Reload? and why do you use “ONLY” Qualifier? 

What is the difference between Cyclic Group & Drill down Group? 

Explain alternate states and where do you use them?