Data Warehousing Basics

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    What is surrogate key ? Where we use it explain with examples?

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    Editorial / Best Answer

    Answered by: saravanan

    • Dec 2nd, 2005

    Surrogate key is a unique identification key, it is like an artificial or alternative key to production key, bz the production key may be alphanumeric or composite key but the surrogate key is always single numeric key. Assume the production key is an alphanumeric field if you create an index for this fields it will occupy more space, so it is not advisable to join/index, bz generally all the datawarehousing fact table are having historical data. These factable are linked with so many dimension table. if it's a numerical fields the performance is high

    Anukul Thawarey

    • Aug 8th, 2017

    Just to add on to this point, we can also have date stamp as in the format (yyyymmdd) which is actually an 4 Byte unsigned integer to keep track of the historical data. This date stamp column can also be considered as an surrogate key.


    • Oct 16th, 2016

    A surrogate key is any column or set of columns that can be declared as the primary key instead of a "real" or natural key. Sometimes there can be several natural keys that could be declared as the primary key, and these are all called candidate keys.So a surrogate is a candidate key.


    What is the difference between Datawarehouse and Datawarehousing

    Dr BK Verma

    • Jul 2nd, 2017

    Data Warehouse: It is just container to store the data from different sources. In this part we can't have right to analysis the data its just storage data. Data warehousing: If we use any intelligent...


    • Jan 25th, 2017

    Datawarehouse: Datawarehouse is a container consists of Subject-oriented, Time variant, Non-volatile and Integrated collection of data which is a Historical data. Datawarehousing: Datawarehousing i...


    What are the Different methods of loading Dimension tables


    • Jun 26th, 2017

    how do you update when customer changed address: on 06-26-2016 -------------- 101,101_address1, on 06-26-2017, customer 101 moved to new loc and 102 added ---------------- 101,101_Address2 ...


    • Jan 25th, 2017

    There are 2 types of data loading.
    1. Initial Loading: Data loading for the first time in to Table/Database is called Initial Loading.

    2. Incremental Loading: Inserting new data and updating existing data which comes with new values is Incremental Loading.


    Give examples of degenerated dimensions


    • Jun 20th, 2017

    Order number, invoice number, POS Transaction number, bill number. These are all examples of degenerate dimension table


    • Feb 2nd, 2013

    A source table has a single column, we not transfer this column to dimension table, directly to connected to the fact table ,this fact table called the de-generated dimensional table


    Can a dimension table contains numeric values?


    • Jun 22nd, 2017

    Yes dimension table can contain numeric value. i.e. Product dimension can have price, quantity as numeric values


    • Aug 17th, 2016

    Yes, A dimension Table can have numeric data types and information. For example. the surrogate key columns which are numeric. and in a scenario if a product has min discount and max discount column...


    Max of Date using Aggregation

    How to find Max and Min of date in aggregation ?

    Empid start_date End_date Sal
    1 2015-01-01 2015-12-31 1000
    1 2016-01-01 2017-05-29 2000
    2 2014-01-01 2015-12-31 1000
    2 2016-01-01 2017-03-15 800
    3 2011-01-01 2015-12-31 1000
    3 2016-01-01 2017-05-10 1200
    4 2016-01-01 2017-02-14 2000

    Output_Should be like...


    What is data cleaning? how is it done?


    • May 25th, 2017

    While loading the data from Source to Target, if we are removing unwanted data or converting inconsistent data to consistent format is data clensing


    • Jan 25th, 2017

    Data Cleansing is the process of converting inconsistent data into consistent data and removing unwanted data.


    What is a Data Warehousing?

    Data Warehouse is a repository of integrated information, available for queries and analysis. Data and information are extracted from heterogeneous sources as they are generated....This makes it much easier and more efficient to run queries over data that originally came from different sources. Typical relational databases are designed for on-line transactional processing (OLTP) and do not meet the...


    What is a lookup table


    • Jan 25th, 2017

    Lookup for some related data in Database or Flatfiles or Database View based on key column

    Johnson Weltch

    • Dec 16th, 2016

    This was great to know more about lookup table in database. You may also go through this informative article on look up table to get brief knowledge about Lookup table in database:
    Lookup table in SQL Server at sqlmvp org


    What is a Star Schema

    Answer posted by Chintan on 2005-05-22 18:34:55: A relational database schema organized around a central table (fact table) joined to a few smaller tables (dimension tables) using foreign key references. The fact table contains raw numeric items that represent relevant business facts (price, discount values, number of units sold, dollar value, etc.)


    • Jan 25th, 2017

    A Fact table is surrounded by multiple Dimension tables and which is look like STAR in graphical design is called "STAR Schema".


    • Sep 16th, 2011

    Star schema defined as,A fact table is surrounded my many multiple dimension tables.
    (it means all dimension tables directly maintains relationship with the fact tables in this schema)


    What is the Difference between OLTP and OLAP

    Answered by swetha on 2005-03-30 12:00:33: OLTP  Current data Short database transactions Online update/insert/delete Normalization is promoted High volume transactions Transaction recovery is necessary   OLAP Current and historical data Long database transactions Batch update/insert/delete Denormalization is promoted Low...


    • Aug 30th, 2016

    OLTP: Original Source of data
    Running on fundamental business task

    OLAP: Data coming from various OLTP sources
    Problem Solving, Decision Making


    • Jan 16th, 2015

    Very useful answer.


    Question about the design

    I am a programmer, VB .NET.
    I have a Question about the design tools in this photo.
    Whether the list box is used?or tree view?
    What tools are used?
    Thank you.


    What is SCD1 , SCD2 , SCD3


    • Feb 20th, 2015

    SCD1: in SCD1, no history is maintained.
    SCD2: whole history is maintained.
    SCD3: just the current and last record is stored.


    • Nov 22nd, 2013

    The value of dimensions is used change very rarely, That is called Slowly Changing dimensions.

    they are 3 types


    scd1:it used Replace the old values overwrite by new values
    scd2:Creating Additional records
    scd3:Its maintain just previous and recent

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