Informatica Interview Question and Answers

1. What is Data warehouse?
  According to Bill Inmon, known as father of Data warehousing. “A Data warehouse is a subject oriented, integrated ,time variant, non volatile collection of data in support of management’s decision making process”.
 
Ramakrishna,said Apr 21, 2014
A data ware house is a RDBMS which is especially desinged for analysis of the busines and making decision to achive business goals, but not for the business transfermation Process. Since desinged for analaysis and dession making hence which is called as DSS(Dession supporting system). since warehouse database preserves historical transaction hence it is called as Historical database. A dataware house is a concept which needs RDBMS to consollidate data from mulitiple oLtps.
Satya, says Feb 06, 2014
DW is a storage place where we can keep/ store historical data related with a particular bussines for future analisys on it or it will support to mgmt to take dicision.
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2. What are the types of data warehouses?
 
    There are three types of data warehouses
  • Enterprise Data Warehouse
  • ODS (operational data store)
  • Data Mart
 
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3. What is Data mart?
  A data mart is a subset of data warehouse that is designed for a particular line of business, such as sales, marketing, or finance. In a dependent data mart, data can be derived from an enterprise wide data warehouse. In an independent data mart can be collected directly from sources.
 
Ramakrishna,said Apr 21, 2014
Data mart is a subset of DW, which is espicailly desinged for paritular business line. Like Healthcare, finance, Marketing, sale. e.t.c we have devided Data mart in two Types. 1 Dependent DataMart 2. Independent DataMart.
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4. What is star schema?
  A star schema is the simplest form of data warehouse schema that consists of one or more dimensional and fact tables.
 
Narasimha,says Apr 13,2014
Star schema is nothingbut fact table is Centralized and surrounded by one or more de-normalized dimension tables. It's look like Star type that is Called Star Schema.
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5. What is snow flake schema?
  A Snowflake schema is nothing but one Fact table which is connected to a number of dimension tables, The snowflake and star schema are methods of storing data which are multidimensional in nature.
 
Soumyadeep, said Feb 22, 2014
Snowflake schema arises out of situations where base dimension tables are classified further into classified attribute dimension tables to reduce the data redundancy, but at the same time they can\'t be joined directly to the fact table instead are related through the base dimension tables.
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