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 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.

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.

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 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?