Wednesday, 11 February 2015

Experienced Data Warehousing Interview Questions and Answers (Page 5)

Below are some important Data Warehouse interview questions which are asked in most MNC company interviews for beginners or professionals.

41. What is a Hash Cluster?

A row is stored in a hash cluster based on the result of applying a hash function to the row's cluster key value. All rows with the same hash key value are stores together on disk.

42. Describe Referential Integrity?
A rule defined on a column (or set of columns) in one table that allows the insert or update of a row only if the value for the column or set of columns (the dependent value) matches a value in a column of a related table (the referenced value). It also specifies the type of data manipulation allowed on referenced data and the action to be performed on dependent data as a result of any action on referenced data.

43. What is schema?
A schema is collection of database objects of a User.

44. What is Table?
A table is the basic unit of data storage in an ORACLE database. The tables of a database hold all of the user accessible data. Table data is stored in rows and columns.

45. What is a View?
A view is a virtual table. Every view has a Query attached to it. (The Query is a SELECT statement that identifies the columns and rows of the table(s) the view uses.)

46. What is an Extent?
An Extent is a specific number of contiguous data blocks, obtained in a single allocation, and used to store a specific type of information.

47. What is an Index?
An Index is an optional structure associated with a table to have direct access to rows, which can be created to increase the performance of data retrieval. Index can be created on one or more columns of a table.

48. What is an Integrity Constrains?
An integrity constraint is a declarative way to define a business rule for a column of a table.

49. What are Clusters?
Clusters are groups of one or more tables physically stores together to share common columns and are often used together.

50. What are the different types of Segments?
Data Segment,
Index Segment,
Rollback Segment
Temporary Segment
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