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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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SCD-2 using delta live table

Delta live table now has the capability to do SCD Type 2 changes. But after going through this feature, I understood that this will work if I have only one new row with a new effective date. In the scenario where I have two new rows with two…
Rajib Deb
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Delta Live Tables using SCD type 1

I'm trying to load data using DLT and SCD 1 and am running into the error message "Detected a data update in the source table at version x. This is currently not supported. If you'd like to ignore updates, set the option 'ignoreChanges' to…
AndyMN
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Delta live tables - Slowly changing dimensions

Is it possible to create an Slowly Changing Dimension mechanism using Delta Live Tables? I would like to implement something like this https://docs.databricks.com/_static/notebooks/merge-in-scd-type-2.html But in the DLT docs i found "Processing…
repcak
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Using MERGE with analytic functions (like RANK) on target table

I have a data pipeline where, at random intervals, the a staging table called stg is truncated and overwritten with records. Then, using MERGE, the records in stg should be merged into the dimension table dim according to the following rules (it's a…
David
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Fact Table Structure Guidance Needed - TSQL

I'm in the process of creating a data warehouse. My dimensions are fairly well-defined: Member, Provider, Claim and Date. My fact table on the other hand is causing me to doubt my design. FactClaimDetail is currently designed as follows: CREATE…
SidC
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How to implement scd type 2 for following

We have data as following: Fact table : id | key | name | salary | loaction | start_date 1 | emp_1 | Shubham | 10000 | Delhi | 1998-02-01 2 | emp_2 | Ashish | 12000 | Pune | 2000-01-01 3 | emp_3 | Shubham | 15000 | Mumbai |…
user14905998
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Generate order number based on a column value with reference to other columns

This is question in Oracle views.I have a table with Emp_id,Start_Period and Key. Sample data is given in Descending order of start period with 201909 on top. Need to generate a column named Key_order. (Finally I am planning to create a view with…
Baby
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T-SQL Slowly Changing Dimension - Multiple Updates, Single Action Output?

I've implemented four SCDs for the warehouse I'm working on and they're working a treat. Hopefully I've understood SCD methods correctly and assuming I have, I now have a bit of an issue I'd like help with. The issue is that there are fields that…
Jeff Scott
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Slowly Changing Dimension Transform in SSIS won't update

I used the following from a CSV to test the SCD. I thought it would recognize the LocationIDs and update the records where necessary. But it did not. It only inserts new records. I'm using Visual Studio 2010 and SQL Server 2012 with Win…
Jacob Pressures
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How to set up primary key, auto increment, and indexes in row versioned MySQL table (SCD type 2)?

For a project I need to implement row versioning in a MySQL database. After reading about the possible solutions I've chosen to use one table and add a start_date and end_date column, that specify when that version/row was active. The id column will…
Jonathan
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Slowly changing dimension - What is Pure type 6 implementation

I am trying to understand pure type 6 SCD implementation from WIKI which says mainly three points Having a Type 2 surrogate key for each time slice can cause problems if the dimension is subject to change. A pure Type 6 implementation does not use…
Shantanu Gupta
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Slowly Changing Dimensions in SSAS and SSRS

I have a project where establishments are inspected anything from once every 6 months to once every 3 years and the results of the inspection scorecard are recorded as a record in a type 2 slowly changing dimension table [tblInspections], using…
Paul Farr
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Issue with inferred member using SSIS Dimension Merge SCD Component

I'm using the SSIS Dimension Merge SCD Component (http://dimensionmergescd.codeplex.com/) and have a situation where I have a configuration with both SCD1 and SCD 2 columns. I have rows where the InferredMember flag is set however the component…
tlum
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Slowly changing dimension type 2 implementation in SSIS

what is the best way to implement the type 2 dimension in SSIS from the following options: 1.using merge statement. 2.using SSIS SCD component 3.using lookup, conditional split(custom way to implement it). could you please give me the detail on it…
user998918
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changing dbt dates names in snapshot

How can I change the default columns name in a snapshot: dbt_valid_from dbt_valid_to? I override the macro default__build_snapshot_table and it is working the first time, but when I re run the snapshot I am getting the following error:
Gladis Carmona Pedraza
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