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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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Unable to select Variable to set date values in SCD type 2 , SSIS

I am creating a SCD type 2 dimension. In my destination table there are start time and d]end date columns. I am unable to select the variable to set date values in the SSIS package. Is this something I should configure in the SSIS package? If so,…
jithmi97
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How to make non-sequential ranges unique?

I am strugling with some T-SQL code to get column [Num] (in below example table). Basically, I am trying to create an index on when a new sequence of [Type] is starting. Q: How to create the [num] field below? [Num] is the order of sequential ranges…
NathSQL
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AWS DMS produces different CDC updates with same CDC timestamp

I have an AWS DMS running with RDS (postgres) as source and S3 CSV as target. Source table has following schema: id: bigint description: varchar The goal is to capture CDC updates into SCD type 2 (or type 2) table. So the original thought was to…
Yurii Oleynikov
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Handling invalid records in fact table after MERGE statement

How do I best handle invalid records in a fact table after a MERGE statement? This is my fact table: schema_name.fact_table This is my dimensional table (SCD2): schema_name.dim_table In my dim_table I have a proper SCD2 with unique surrogate keys…
G0000000se
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Changing the SQL generated by DBT

Looking for some guidance, pointers about building SCD2 dimension using DBT's snapshot. Few specific things that I am looking at How to change the generated SQL so that dbt_valid_from, dbt_valid_to columns are named start_date, end_date (I can build…
user3138594
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SSIS Slowly changing dimension column

I'm using a Slowly Changing Dimension in SSIS and I'm using a single column called active of type BIT to determine the latest records instead of start date and end date column. My problem is the following: I want to turn the active value to 0 for…
Selim Bamri
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How scdtype behaves when we have a new column added to the source table?

We have built models for our project and it was running fine. We have scdtyp2 models created , incremental models created having all the required data. Issue is occuring when we have a new column being added to the source table.When running the dbt…
Game Changers
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SCD Start and End Date

I am new to ssis and i am a little bit confused about the SCD_Start_Date and SCD_End_Date when we use the SCD dimension wizard. on many examples that i have searched online people always use the "system start time" or "system container " start…
rafamaniac
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How to turn SCD type 4 into type 6

I am working with a data model (in a data mart) that has a type 4 slowly-changing dimension. The implementation is unlike what I typically see. The model looks like: (If not clear, the issue is that DimProductHistory is not part of the fact…
skyline01
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How can I specify the start and end dates for SSIS SCD type 2 wizard instead of variables

I'm trying to create a dimension table using SSIS but I'm having trouble creating an SCD type 2. I have a staging table with a business key column, a value column I want to track historical and start and end dates when changes occurred. I am using…
mobcdi
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What should happen to a SCD 2 table record if the record becomes inactive?

Let's say we have a table that has these values: id| name| country| start_dt| end_dt| is_current| current_dt 1001| John| CA| 2001-01-10| 2012-06-01| TRUE| 2012-06-01 Next day, the same record comes from upstream and the SCD2 record modifies to: id|…
Parijat Bose
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Parsing a Type 4 Nested Parquet and flattening/Explode JSON values in a column in pyspark

I am relatively new to Pyspark. And for orchestration I use Databricks. [Just FYI: My source Parquet holds a SCD Type 4 dataset where the Current Snapshot and History of it is maintained in a Single row, where the Current Snapshot is in Parquet…
Aaron
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SQL Server: Slowly Changing Dimension Type 2 on historical records

I am trying to set up a SCD of Type 2 for historical records within my Customer table. Attached is how the Customer table is set up alongside the expected outcome. Note that the Customer table in practice has 2 million distinct Customer IDs. I tried…
Aiden Aslam
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Can a SCD 2 table have non SCD columns?

Lets say there is a table schema where in the columns are a,b,c,d,start_time,end_time,current_status. Can we have a,b,c as SCD columns and let d not be a part of SCD logic so that if d changes, it wont create a new SCD row?
Parijat Bose
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How to copy a date from one row to another with matching (SCD Type 2)

I've been struggling to write a query in SQL that sets the start_date of the company's new license plan to be equal to the expiration date/end_date plus one day of the company's previous license plan. In the image below you can more clearly see what…
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