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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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implementing scd type 2 as a generalized stored procedure in azure data warehouse for all dimensions?

I am new to azure and I am working on Azure data warehouse. I have loaded few dimensions and staging tables. I want to implement SCD type 2 as a generalised procedure for all the updates with hashbytes. As we know, ADW doesnt support merge, I am…
Monsta
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Performance of joining SCD Type 2 tables in Hive

I have a 2 tables in Hive which are managed using SCD Type 2 (https://en.wikipedia.org/wiki/Slowly_changing_dimension#Type_2:_add_new_row). Basically, each record has 2 columns valid_start_date and valid_end_date to specify the period during which…
Nguyen Nguyen
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Historical data sets in an initial build

The issue I am currently facing is I think a logical one and maybe a limitation of SSIS. My data has a set of accounts, at any point this account can be owned by an organisation. This combination controls my historical dimension of "Account" E.g…
Caz1224
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SCD type 2 including Version Counter every time a record changes

I want a +1 counter for my slowly changing dimension DIM_Object. Every time when a record from the table PMEObject table changes, I want DIM_Object.Versie to increase by 1. Everything about the code works fine, this can also be run without any…
Ad van Dorpen
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How do I enforce referential integrity on a type 6 SCD Dimension table?

I'm having difficulties with designing the Primary and Foreign key relationship between my fact table and a Type 6 SCD Dimension table. The dimension table has the following definition: CREATE TABLE DimTable ( surrogate_key INT, row_key …
sndekoning
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How to track merging in Slowly Changing Dimension and Facts

In a datamart where 2 or 3 or more dimensions merge to form a new dimension. How can the scd be managed to keep track of all mergers historically and present trending facts as related to those dimensions? A specific example would be three stores…
Faisal Majeed
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Update a Record in a SCD2 Table

I have a table in which the entries are historized with SCD 2 the table look like this: PK ValidFrom ValidTo 635582110901 04.01.2016 21.01.2016 635582110901 22.01.2016 26.01.2016 635582110901 27.01.2016 …
AmBlack
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Query SCD type 2 table in MySQL

Imagine the following table: ID Name Type Start_Date End_Date 1 Cust_1 Retail 01/01/2010 21/07/2010 1 Cust_1 Oher 22/07/2010 17/05/2012 1 Cust_1 Corp 18/05/2012 31/12/9999 I would to know if there's any way to build a…
Ricardo Adão
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Slowly Changing Dimension: Update "row is current" value

I have a customer SSIS package that is configured to be a slowly changing dimension. During the wizard, when choosing either the is current or the start-end date option, I have chosen the start and end date options. I also have a column called…
TomLenzmeier
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Best practices for using SCD component in Talend

I am using tPostgresqlSCD. The performance is really slow. It inserts 1 row per second or even slower. Is there anyway to increase the peformance of it? I tried 'Use memory saving modes'. Which makes it even slower. I am inserting around 9000…
jmf
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SQL Server - How to Use Merge Statement for Slowly Changing Dimension with More Than Two Conditions?

I am trying to implement Slowly Changing Dimension Type 2 through T-SQL but I can't figure out how to put a request to work. Table columns: cpf, nome, telefone_update, endereco_insert Basically the logic is: if the MATCH doesn't happen using cpf,…
Lucas Rezende
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Postgres Indexing

I am a newbie in Postgres. We have implemented SCD type-2 in our project using Postgres. The input file is a full refresh file with approximately 30 million records daily. Account number is the key column. The approximate number of new records will…
Bagavathi
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Which is the best approach for a dimension (SCD-2 or a SCD-1 + a whole new dimension)

Let´s say I have the following situation: A dimension Product with some attributes that aren't volatile (Description and Diameter - they can only be changed by a SCD-1 change for correction) and a attribute that can be volatile (Selling Group, it…
Sawd
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Datawarehouse Number of records timeline

I don't have historical information on sales order in my ERP database. I have a table containing sales order. Once a sales order is approved, it is transformed in an invoice and the record sales order is deleted. I can code in the ERP a historical…
Knutov
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SSIS Slowly Changing Dimension Historic Attribute

this is a simple SCD with a type two (historic) change available. In the image, when a row is updated, two distinct rows exist, one that travels down the 'New Output' path and one that travels down the 'Historical Attributes Inserts Output'. …
ivan7707
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