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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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Changing Properties of a Slowly Changing Dimension Transformation in SSIS

I have a problem with changing the properties of the SCD transformation in SSIS 2005. I can define all the properies and mappings the first time i edit the transformation and its working. But when i open the property editor of the component again,…
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Azure Databricks Delta Live Table stored as SCD 2 is creating new records when no data changes

I have a streaming pipeline that ingests json files from a data lake. These files are dumped there periodically. Mostly the files contain duplicate data, but there are occasional changes. I am trying to process these files into a data warehouse…
Kearon McNicol
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Optimal query/join for joining scd-type-2 dimension with facts for reporting/aggregation

I have a fact table and an scd-type-2 dimension table. I want to produce sales report by region and year. I have working solution with a query that joins them for reporting purposes. When I run the query in spark/databricks, it gives me a little…
Kashyap
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Converting EAVT table into SCD type 2

After a lot of research and head picking, I'm still unable to find a good/clean solution to convert an entity-attribute-value-timestamp table to an scd type 2 dimension. Here's the issue: I have a CRM source that stores all history in a EAVT model…
Rami Ouanes
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What is the difference between storing the changing value in fact vs dimension?

I have customer dimension table and the location of customer can change. The customerid filters the sales fact table. I have 2 options: Slowly changing dimension type 2 to hold 1 new record for each customer's location changes Or Store the…
variable
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Implementing Revisioning with SCD2/4

I'm working on a project that is a sort of bill of materials manager that needs to support revisioning of components. After some research, I've stumbled upon slowly changing dimensions type 2 and type 4 which seems like the most appropriate pattern…
user1960118
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Can't use SCD component because of identity column

I have a fact table and a dimension table. dimension table uses identity as id column and that id is in the fact table for relation. In the ssis, scd component doesn't see my id row on dimension as business key, how can i do scd, what should i…
Hacktan
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Creating SCD type 2 with SQL

I am trying to create a SCD type 2 table in SQL server for a data warehouse. I am using the MERGE statement, and my problem is with the "When Matched" part. For example: I have a certain customer that moved from Miami to New York. I would like to…
Tal Cordova
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SCD Type 2 merge logic resulting in duplicates in destination table

I am trying to implement SCD Type 2 merge logic in big query. I am doing this in 3 setup approach but every time i run my merge logic script but it seems to push records into my destination table even if there is no new record. Step 1: when records…
prasanna kumar
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Update Snowflake table

I am trying to update snowflake table via databricks. where i have created databricks temp table and created query based on temp table which will update snowflake table. But i am not sure if it is possible at all Could someone help me on this. query…
SunithaM
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SQL Summary of Status total values by Month of Type2 SC Dimension

I have a voucher status history table as a type2 slowly changing dimension table I am trying to get the summary total value of each status by each month before a particular date. This is my schema and insert code: CREATE TABLE #HDimVouchers( …
Paul
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How to open a .scd2 type file

I have first time encoutered a .scd2 type file. I downloaded this file from a sensor database. And I need to view the measeurements to make analysis of te data. I know SCD means slowly changing dimensions but I have no idea how to open this type of…
Murtaza
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Am I implementing SCD type 1 & 7 correctly

SCD type 1 Suppose I've built SCD type 1 over the following data that comes from operational system: ID | CHANNEL_CODE | NAME | TYPE 1 | A | X | 0 2 | B | Y | 1 Because, Surrogate Keys are preferable even for SCD…
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What is the best way to make SCD Type 2 table from streaming replication data?

Usually SCD Type 2 implemented using ETL but is it possible to do this using realtime data processing, like for example Spark Streaming or KSQL?
ant0nk
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Data warehouse and changing dimensions

I am fairly new to data warehouses and I want to make sure my plan makes sense. I am using a star schema to capture insurance information for reporting purposes. The users want to see everything as-of a specific day, since ever field can change…
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