Data Warehousing Interview Questions

Usually Surrogate keys are System Generated keys that can be used in place of missing primary key.

A surrogate key in a database is a unique identifier for either an entity in the modeled world or an object in the database. The surrogate key is not derived from application data. A surrogate repres...

Data Marts are considered as smaller logical subset of Data warehouse. DW is enterprise-wide while DMs are for Department Level. So DMs can be identified on the basis of what departments are there in Insurance company.
E.g. Sales Department.

Here are some questions... (I am assuming that you are asking about Informatica data quality) 1. What are the most used transformations in IDQ? 2. What is address doctor? 3. Can we export an object fr...

Interview questions for Data Quality Analyst are as follows:
1. How can you say there are no duplicate records in Data warehouse?
2. Whether the ETL job accepts known accept records?
3. What are the Data Quality Tools? e.g. BO Data Quality, First Logic..etc

Bill Inmon's paradigm: Data warehouse is one part of the overall business intelligence system. An enterprise has one data warehouse, and data marts source their information from the data warehouse...

A degenerate dimension is a dimension which is derived from the fact table and doesn't have its own dimension table.

Example : Receipt number is the perfect example for degenerate dimension.

This is a process and outcomes of modeling a logical database schemas created to support OLAP and data warehousing solutions.

Here's a different way to look at dimensional modelling:Consider data to be a flat table for now. It would have some columns that contain numbers that need to be used in calcualtions later (e.g. b...

I am not sure if this pertains to the datawarehouse in general but we do have concept of audit dimensions. Also, dimensions with effective dating can help tracing the changes.

I guess, this question should be directed towards particular tools... as a concept, data warehousing would be hard pressed to have any logging...

Customer dimension is a good example. Customer address and Phone number frequently changes. So you will update the customer dimension for these changes.Hence its called as SCD. There are several types though. This example is type1 SCD.

Visualize it...You need more lookup data to fit in a single row in dimensions.. Its lookup data, it wont have as many records as the fact, but it would have far more columns. A Visually, if you think...

A dimension table contains details about subject area. Eg. customer , product

Fact table contains all business measures ( numeric value) and foreign key value.

Always integer or numeric

Surrogate keys are the system generated keys and used to eliminate the redundancy in the primary keys. So they are always integer numbers.

Star Schema: 1. Dimension tables directly connected to Fact Table2. Contain de-normalized data3. Data modifications are very easily4. Highest flexibility5. Best performance6. Takes more memory space t...

STAR SCHEMA HAS fact table linked with dimension table directlywhile in snow flake schema the dimension tables can have futher hierarchies between them .it means in snow flake schema the tables are no...

Database is the root of any data releted operations where as datawarehousing is a schema or process how effectively we access or utilize a database. Datawarehousing follows the star schema and snowflake schema as its basic schemas and we two other schemas also which are not much important.

Database: A database is used to record, retrieve, update business transactions which are occurred daily in business life. Data ware House: A data warehouse is used to record historical data, purely for analysis purpose for top management.

An Operational Data Store (ODS) is a repository of active "operational" data.  It's typically used to hold data for a short period (eg. Days or weeks at most), to help the business ...

Stagining and operational data store are different databases.It can be one database aswell to reduce the cost to maitain two databases.Staging is the place where cleansing is done and Operational Stor...

Data cleaning, technically called "Data Cleansing"is a group of methods for making data more reliable and accurate. Usually companies store data in warehouses so they can make meaning out of...

Data cleaning is a self explainatory term. Most of the data warehouses in the world source data from multiple systems - systems that were created long before data warehousing was well understood, and ...

We use OOAD in order to design the system when overall requirements needed for developing the new system are clearly understood by the developer.

Data marts are part of OLAP system. Data in datamarts cannot be trasient. Data will be updated in datamarts on a periodic or daily basis depending on the design of the data warehouse.
-Ashish

A DW is no longer relevant when it contains inconsistent data. The strength of a DW - and its robustness - also relies on the validation processes... The sooner you can detect and report any inconsist...

One of the main purpose of Datawarehousing is to get Cleanse data.
So skipping data validatons is not a good idea.
It will be better to bring the data to a staging area and perform validations.
Or while pushing data from the source we can perform data validations.

Correct me if i misunderstood your question. I think you want to know whether the usage data will improve the graph performance. I think definitely the usage of data will definitely improve the graph ...

As the definaton of Datawarehouse say it is repository of historial data which is used by Busines users to run some reports on his/her area of interests.Data is not loaded everyhour or every mtes in D...

No, a data warehouse cannot by definition be used as a transaction database.  A data warehouse is "read only" data that does not change once it has been loaded and used for informa...

Mapping parameter are the constant values (values never changes) and mapping variables are the values that ever changes.

A mapping parameter is a static value that you define before running the session and it retains the same value till the end of the session. Define a parameter in paramaeter file (.par) and use it in m...