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Questions tagged [scd]

Slowly Changing Dimensions or Schema Component Designator

SCD may refer to Slowly Change Dimension transformation for SQL Server or Schema Component Designators which is a declarative query language for XML Schemas.

Slowly Changing Dimensions in data management and data warehousing are relatively static dimensions containing entities. Data captured by SCD changes slowly rather on unpredictable time interval. In the data warehouse they are used for reporting historical data.

Slowly Changing Dimension Techniques :

  1. Type 0 - retain original. Dimensions attributes never change, so facts are always grouped by original value.
  2. Type 1 - overwrite. The old attribute value in the dimension is overwritten with the new value.
  3. Type 2 - add new row. It adds a new row in the dimension with an updated attribute values.
  4. Type 3 - add new attribute. It adds a new attribute in the dimension to preserve the old attribute value.
  5. Type 4 - add mini-dimension. When a group of attributes changes rapidly and it split off to a mini-dimension.
  6. Type 5 - add mini-dimension and Type 1 outtriger. Used to accurately preserve historical attributes values, plus report historical fact according to current attribute value.
  7. Type 6 - add Type 1 Attributes to Type 2 Dimension. Like Type 5, Type 6 delivers both historical and current dimension attribute values. Type 6 builds on the Type 2 technique by also embedding current type 1 versions.
  8. Type 7 - dual Type 1 and Type 2 dimensions. Final hybrid technique used to support as-was and as-is reporting.

More information on Slowly Changing Dimensions:

  1. Kimball Dimensional Modeling Techniques
  2. Wikipedia
  3. Slowly Changing Dimensions by Ralph Kimball
  4. Slowly Changing Dimensions Are Not Always as Easy as 1, 2, 3
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Slowly changing Dimension always updating

I have a dimension to load which has a field called description with a data type of VARCHAR(50). Its collation is SQL_Latin1_General_CP1256_CS_AS and it contains Arabic data such as "مركز العقبة". Its source has the same type, size and collation,…
Osama Shatnawe
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Loading a database table with "slowly changing dimensions" in Python

Ok, I can load records into a table using to_sql in pandas. (Unfortunately, I cannot use bcp or bulk insert, because my (SQL Server) database server is remote). How about a table with (Type 2) slowly changing dimensions? In SSIS, I would use SCD…
Dimitri Shvorob
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audit table vs. Type 2 Slowly Changing Dimension

In SQL Server 2008+, we'd like to enable tracking of historical changes to a "Customers" table in an operational database. It's a new table and our app controls all writing to the database, so we don't need evil hacks like triggers. Instead we will…
Justin Grant
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JAXB generated classes of certain types implementing a custom interface

I am working on an application that uses XJC to generate Java POJOs from XSDs. There are dozens of schemas, and that number will grow. The application also needs to be able to handle different versions of the same schema, which means that I will…
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SQL Query for SCD Type 2

I am given the following table with the following problem: Create a Slowly Changing Dimension Type 2 from the dataset. EMPLOYEE table has daily records for each employee. Type 2 - Will have effective data and expire date. Employee…
LukeThomas
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Type II SCD with entities that merge over time

Let's say we have a dimension that represents sales offices. The offices might move, which would be a type II change. We'd want to track operations that happened at the old office location, and operations that now happen at the new, and know when…
siride
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Handling Deletes in SCD Type 2

As a Modeler trying to find out what is the best way to handle deletes in SCD Type 2 tables. As per principle an SCD Type 2 table is to track changes using ETL dates like START_DT and END_DT. START_DT will be the date the record is effective…
Ankit Srivastava
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Understanding slowly changing dimension (SCD) type 5 and 7 with examples

I'm trying to understand how SCD Type 5,6 & 7 work. I read this article of Kimball Group and stack overflow answer on Type 6. I could understand Type 6 concept, how it works and when to use it. However, I'm still unable to understand how type 5 & 7…
Ash
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How to handle Slowly Changing Dimension in Amazon Redshift using Pentaho?

Since Amazon Redshift is optimized for reading instead of writing, how can I manage a Slowly Changing Dimension procedure using an ETL tool, in my case Pentaho Data Integration? As the ETL tool would do updates/inserts (Dimension Lookup/Update) line…
Lucas Rezende
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Best practice for SCD date pairs (closing / opening timestamps)

When implementing temporal datetime pairs, which is the better approach? Approach 1 _RK FROM_DTTM TO_DTTM 1 01-JAN-2012 00:00:00 31-DEC-2012 23:59:59 ------------> Old record closed out 1 01-JAN-2013 00:00:00 31-DEC-4949…
Allan Bowe
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Create rows in sql join with overlapping date ranges

I have two tables as below: TableA ID link1 link2 DATE_FROM DATE_TO 99 H J 1999-01-01 2005-01-01 TableB ID link1 link2 DATE_FROM DATE_TO 99 X Y 2002-01-01 2008-01-01 And I want to query them and retreive the result…
ezryder
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SSIS :: How to implement SCD type 2 in SSIS without using SCD Wizard. When incoming dataset has multiple records for the same Business Key

In SSIS, if an incoming dataset has multiple records for the same Business Key, how do I load it to the dimensions table with SCD type 2 without using the SCD Wizard. Sample dataset Customer ID Name Segment Postal Code 1 James…
Saurav Kumar
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Optimizing SCD2 JOINS in Postgres

Right now I'm working on developing a DB schema for an application which requires versioning several different sets of numerical data which must be joined together for use in views. The application requires that we're able to 'look back' and find…
ajxs
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Data Warehouse - Slowly Changing Dimensions with Many to Many Relationships

As an example, let's say I have a fact table with two dimensions and one measure FactMoney table ProjectKey int PersonKey int CashAmount money The two dimensions are defined like this: DimProject (a type 0 dimension - i.e. static) ProjectKey…
Scott Herbert
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SQL INSERT, UPDATE and DELETE based on source table

I have a source table with fields ID NAME and DESIG create or replace table emp_source ( id number, name string, desig string ); And my destination table has columns ID NAME DESIG META_CRT_DT (date when record is inserted) META_UPD_DT…
TrenT
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