What is Synthetic Key?

Synthetic Keys: when two or more tables have two or more fields in common is called synthetic key. 

Below are the ways to remove synthetic keys

• Join
• Alias
• Concatenated key
• Link table
• Qualify

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…)

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.

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 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?