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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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If i have an large SCD2 dimension in snowflake with high and sparse churn, is there a way to end date old rows efficiently?

I have a SCD2 dimension in our snowflake implementation, something like this DEAL_SIDE_LEG_DIM DIM_DEAL_ID Number Surrogate PK DEALNO Business key DEALSIDE Business key DEALLEG Business key various attributes VALID_FROM date VALID_TO date NB -…
Matt Prince
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is this a Valid approach for SCD type2 implementation in spark without using delta lake?

Approach: Assuming there are 2 DataFrames daily and target with same columns, target DataFrame is also having previously expired records. target=spark.read.table('target_db.target_table') active=target.filter(col('record_Status')=='active')\ …
Lambda-Square
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Slowly Changing dimension type 1 in SQL server - deleting data on target table

Hei, I am new to SQL so my apologies if this question is too basic. I have a solution with the following tables and logic for SCD Type 1. -- Source table CREATE TABLE table_source ( recipe_id INT NOT NULL, recipe_name VARCHAR(30) NOT NULL, HashValue…
db_noob
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SCD0 implementation using staging and taget table

I'm looking for a one transaction query that would allow me to truncate a target table first and insert everything from staging table to target table. I tried using merge into, but that requires using keys and is not very generic. Any thoughts?
Aleksander Lipka
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Developing Slowly Changing Dimension in SSAS

I searched the internet a lot but nothing good came of it. I have 3 table and want to develop SCD type 2 in SSAS Cube. 1- DimCompanies 2- DimDate 3- FactTable FactTable: Val CompanyId DateId DimCompanies has this information…
mahdi moghimi
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Capturing Insert ,Update and Delete counts from Merge

I use the below T-SQL Merge statement to perform incremental load data from transactional database into Data Warehouse. This Merge statement loads data as a SCD Type 2 and it works well. --Begin handling SCD2 changes INSERT INTO …
Peter Nguy Nguyen
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Create Slowly Changing Dimension (SCD) Type 2 from the Given Table

I'm trying to create a SCD type 2 from the table below using SQL. click on table for better visibility if neededAs shown, The table has daily records for each employee. I want to create a type 2 that will contain an effective date and expiration…
LukeThomas
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Pivot/Denormalize Over Effective Ranges

I'm looking to pivot a transactional data set into SCD2 in such a way that captures the intervals in which each combination at the pivot grain were effective. Snowflake is the actual DBMS I'm using, but tagging Oracle too because their dialects are…
Error_2646
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Can power bi create a scd from a table with no historical data?

Can creating a temporal table be done in Power bi instead of SQL? I want to import data from my organizations employee database(which overwrites changes so there is no historical data). Compare it in power bi to the table I currently have loaded…
user9456994
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How to map varchar(max) column in SCD transform while doing ETL process in SSIS project?

In Source table AAT_TECHNICIAN column has datatype varchar(max) and in destination dimension table having column TechnicianName with datatype varchar(max) then SCD transform done to load from source to destination. After execute package error…
Sunil Baliyarsingh
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Different SCD types for different columns

Does it make sense to have different SCD types for different columns at single dimension? Or it's always better to split a dimension table into two tables? For example, the operational systems sends me the following data: ID | CHANNEL_CODE | NAME |…
VB_
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Oracle - SCD Type 2

I am new to Oracle. I have 2 tables called. dwh_tbl_dim_supplier_type2_ar (target table) stg_tbl_dim_supplier_ar (source table) dwh_tbl_dim_supplier_type2_ar contains six columns SUPPLIER_KEY…
Ardan
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How to Update Table in Snowflake using Azure Data Factory

I have two tables in snowflake named table1 and table2. Table1 is the source table which contains incremental data and table2 is the target table. So my usecase is I have to take data from table1 and update the data into table2 but this process has…
Vipendra Singh
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Implementing SCD 2 in Informatica without PK defined on the target

How can we implement SCD 2 in informatica when no PK is defined on target table(oracle)? Implementing SCD type 2 using Dynamic lkp concept which will tag the incoming row as 0,1,2. Ive associated the SRC ports to the lookup ports and given the…
Bastian
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.NET ORM Framework with data versioning (Slowly Changing Dimension Type 2)?

I am building a .NET application for inserting data (an Excel add-in in fact), and I want to use an ORM for inserting data with automated versioning. Here's a worked example: User "John Doe" does the first data insertion (4 data points as per below…
vale_p
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