What are some approaches to handling slowly changing dimensions?
We can implement slowly changing dimensions (SCD) using various approaches, such as;
- Type 0: Always retains original.
- Type 1 : Keeps latest data, old data is overwritten.
- Type 2 : Keeps the history of old data by adding new row.
- Type 3 : Adds new attribute to store changed value.
- Type 4 : Uses separate history table.
Which dimension is slowly changing?
What is a Slowly Changing Dimension? A Slowly Changing Dimension (SCD) is a dimension that stores and manages both current and historical data over time in a data warehouse. It is considered and implemented as one of the most critical ETL tasks in tracking the history of dimension records.
How do you handle rapidly changing dimensions?
Fast Changing Dimension Handling
- Identify the fast changing columns in dimension.
- Split the fast changing columns to a separate junk dimension.
- Map the junk dimension with the main dimension using mini-dimension.
What is the difference between ETL and ELT?
ETL transforms data on a separate processing server, while ELT transforms data within the data warehouse itself. ETL does not transfer raw data into the data warehouse, while ELT sends raw data directly to the data warehouse.
What are dimension and fact tables?
Fact Table vs Dimension Table Comparison Table
| Characteristics | Fact Table | Dimension Table |
|---|---|---|
| Creation Time | A fact table is created after dimension tables are created. | The dimension table needs to be created first. |
| Schema Structure | There is less number of fact tables in a schema. | There is a number of dimension tables in a schema. |
What is role playing dimension in data warehouse with example?
A table with multiple valid relationships between itself and another table is known as a role-playing dimension. This is most commonly seen in dimensions such as Time and Customer. For example, the Sales fact has multiple relationships to the Time query subject on the keys Order Day, Ship Day, and Close Day.
How can we implement slowly changing dimension in Talend?
How does SCD type 2 work?
- scd_start: start date of the records activity.
- scd_end: end date of the records activity.
- scd_version: version of the record. Each time the record is updated, the version increases by one.
- scd_active: flag to indicate whether the record is active (current) or inactive (historical)
What is a rapidly changing dimension?
A dimension is a fast changing or rapidly changing dimension if one or more of its attributes in the table changes very fast and in many rows. Handling rapidly changing dimension in data warehouse is very difficult because of many performance implications.
What is ELT example?
For example, an ELT tool may extract data from various source systems and store them in a data lake, made up of Amazon S3 or Azure Blob Storage. An ETL process can extract the data from the lake after that, transform it and load into a data warehouse for reporting.
Is Snowflake an ET or ELT?
Snowflake supports both transformation during (ETL) or after loading (ELT). Snowflake works with a wide range of data integration tools, including Informatica, Talend, Fivetran, Matillion and others.