GeekInterview.com
  I am new, Sign me up!
 
GeekInterview.com  >  Interview Questions  >  Data Warehousing  >  ETL
Go To First  |  Previous Question  |  Next Question 
 ETL  |  Question 61 of 65    Print  
Clean Data before Loading
Why is it necessary to clean data before loading it into the Warehouse


  
Total Answers and Comments: 1 Last Update: June 07, 2009     Asked by: riyazz.shaik 
  
 Sponsored Links

 
 Best Rated Answer
—

No best answer available. Please pick the good answer available or submit your answer.
June 07, 2009 00:05:45   #1  
SQLGal Member Since: October 2008   Contribution: 9    
RE: Clean Data before Loading
Warehouse data is used as source data for data analysis and reporting. The data is organized into groups and categories (aggregation) and then summarized upon those groups (dimensions). These groups are based upon exactness.

For example "house" "houses" and "home" would fall into groups because they are not exact. But logically they are the same and should be of the same group. The process of data cleansing would correct this. This is only one example of data cleansing.


The point is that if data is not cleansed then the resulting reports and OLAP cubes will contain too many categories making them hard to read. The results would also be skewed because factual data (totals counts etc) would be distributed across the good and bad categories. Once loaded into the data warehouse it is very difficult if not impossible to change.


 
Is this answer useful? Yes | No

 Related Questions

Answered by Laxmi on 2005-05-13 16:42:53: Staging area is place where you hold temporary tables on data warehouse server. Staging tables are connected to work area or fact tables. We basically need staging 
Latest Answer : The staging area is:- One or more database schema(s) or file stores used to “stage” data extracted from the source OLTP systems prior to being published to the “warehouse” where it is visible to end users.Data ...
Latest Answer : Client:-* GUI/Presentation logic* Query specification* Data Analysis* Report formatting* Data accessApplication/Data Mart Server:-* Summarizing* Filtering* Meta Data* Multidimensional view* Data accessDW Server:-* Data logic* Data services* Meta data* ...
Latest Answer : You cannot use Informatica to extract data from SAP via ABAP.  Only the SAP/Business Objects Data Integrator product can do this.Informatica uses a data dictionary interface, with clear SQL instructions, example...select BUKRS, BELNR, GJAHR, BUZEI ...
Techniques of Error Handling - Ignore , Rejecting bad records to a flat file , loading the records and reviewing them (default values)
Latest Answer : ODS is nothing but operational data source. It contains  most recent data .it contains around 30-60 days data  It is placed in between source system and staging area..   reports can also be taken in ODS . ...
Read Answers (7) | Asked by : kumar
What are the various test procedures used to check whether the data is loaded in the backend, performance of the mapping, and quality of the data loaded in INFORMATICA.
Read Answers (3) | Asked by : Andy
I'am new to SAS, can anybody explain the process of extracting data from source systems,storing in ODS and how data modelling is done.RegRam
Read Answers (3) | Asked by : ram_sas
Latest Answer : By enablign sorted input property in Aggregator Properties ...
Read Answers (1) | Asked by : srujen
How you capture changes in data if the source system does not have option of storing date/time field in source table from where you need to extract the data?
The DW database can be Oracle or Teradata. The requirement here is to pull data from source system and ETL need to device a mechanism to identify the changes or new records. The source system can be a 
Read Answers (1) | Asked by : GeekNo1
Latest Answer : Like ETL SPEC,they create a document containing the source table (Schema name) and a target table (another schema name) with the logic used in transforming source to target. We have to write database query with the logic contained in the document using ...
Read Answers (2) | Asked by : suma

 Sponsored Links

 
Related Articles

Breaking up XML into Relational Data

Breaking up XML into Relational Data While the preceding example shows how to construct an XML representation over relational data the example in this section illustrates how you can shred XML data back into relational data This reverse operation can be useful if your application works with relation
 

Querying Data with Oracle XQuery

Querying Data with Oracle XQuery Starting with Oracle Database 10g Release 2 you can take advantage of a full featured native XQuery engine integrated with the database With Oracle XQuery you can accomplish various tasks involved in developing PHP Oracle XML applications operating on any kind of dat
 

Retrieving XML Data

Retrieving XML DataTo retrieve XML data from an XMLType table you can use a SELECT SQL statement just as you would if you had to query a relational table For example to select the employee with the id set to 100 from the employees XMLType table discussed in the preceding section you might issue the
 

Using XMLType for Handling XML Data in the Database

Using XMLType for Handling XML Data in the Database Being an object type XMLType can not only be used to store XML data in the database but also to operate on that data via its built in methods Regardless of the storage model you choose XMLType provides a set of XML specific methods to operate on XM
 

Using Oracle Database for Storing, Modifying, and Retrieving XML Data

Using Oracle Database for Storing Modifying and Retrieving XML Data With Oracle XML DB you have various XML storage and XML processing options allowing you to achieve the required level of performance and scalability One of the most interesting things about Oracle XML DB is that it allows you to per
 

ODP.NET - Techniques to Improve Performance while Retrieving Data

ODP NET Techniques to Improve Performance while Retrieving Data Performance tuning is a great subject in Oracle Volumes of books would not be enough to cover every aspect of performance tuning in Oracle However in this section we will only discuss the fundamental performance techniques while working
 

ODP.NET - Populating a Dataset with a Single Data Table

ODP NET Populating a Dataset with a Single Data Table A dataset is simply a group of data tables These data tables can be identified with their own unique names within a dataset You can also add relations between data tables available in a dataset mosgoogle The following code gives you the details o
 

ODP.NET - Retrieving Typed Data

ODP NET Retrieving Typed Data While retrieving values from OracleDataReader we can extract information available in individual columns of a particular row either by using column ordinal position values or column names mosgoogle Retrieving Typed Data Using Ordinals ODP NET provides data specific enum
 

ODP.NET - Retrieving Data Using OracleDataReader

ODP NET Retrieving Data Using OracleDataReader OracleDataReader is simply a read only and forward only result set It works only if the database connection is open and it makes sure that the connection is open while you are retrieving data As the data that it retrieves is read only it is a bit faster
 

ODP.NET - Fundamental ODP.NET Classes to Retrieve Data

ODP NET Fundamental ODP NET Classes to Retrieve Data To retrieve data from an Oracle database using ODP NET we need to work with a few of the ODP NET classes At this point we will discuss the most fundamental classes available in ODP NET for retrieving data mosgoogle The following is the list of fun
 

About Us -  Privacy Policy -  Terms and Conditions -  Contact -  Ask Question -  Propose Category -  Site Updates 

Copyright © 2005 - 2009 GeekInterview.com. All Rights Reserved

Page copy protected against web site content infringement by Copyscape