Quick Answer: What Are Junk Dimensions?

What are different types of dimensions in data warehouse?

Following are the Types of Dimensions in Data Warehouse:Conformed Dimension.Outrigger Dimension.Shrunken Dimension.Role-playing Dimension.Dimension to Dimension Table.Junk Dimension.Degenerate Dimension.Swappable Dimension.More items…•.

How many types of dimensions are there?

A dimension table typically has two types of columns, primary keys to fact tables and textual\descriptive data.

What are dimensions in ETL?

The Dimension Attributes are the various columns in a dimension table. Dimensions offers descriptive characteristics of the facts with the help of their attributes. No set limit set for given for number of dimensions. The dimension can also contain one or more hierarchical relationships.

What are the two basic types of dimensions?

There are two classifications of dimensions: size and location.Size dimensions are placed in direct relationship to a feature to identify the specific size.Location dimensions are used to identify the relationship of a feature to another feature within an object.

What is rapidly changing dimension?

Rapidly changing dimensions are dimensions where the attribute values of the dimension change frequently causing the dimension grow rapidly if you a have designed the dimension to capture the changes as a Type 2 dimension.

What is difference between star and snowflake schema?

Snowflake Schema is also the type of multidimensional model which is used for data warehouse. … In star schema, The fact tables and the dimension tables are contained. While in snowflake schema, The fact tables, dimension tables as well as sub dimension tables are contained.

What is the difference between conformed dimension and role playing dimension?

More details: A database dimension is a collection of related objects, called attributes, which can be used to provide information about fact data in one or more cubes. … A database dimension can be used multiple times in a cube. Those referenced and renamed for purpose database dimension is role-playing dimension.

What is type 1 and type 2 dimension?

In a Type 1 SCD the new data overwrites the existing data. … You do not need to specify any additional information to create a Type 1 SCD. Type 2 SCDs – Creating another dimension record. A Type 2 SCD retains the full history of values.

Which are the dimensions?

The world as we know it has three dimensions of space—length, width and depth—and one dimension of time. But there’s the mind-bending possibility that many more dimensions exist out there. According to string theory, one of the leading physics model of the last half century, the universe operates with 10 dimensions.

What is fact and dimension?

Facts and dimensions are data warehousing terms. A fact is a quantitative piece of information – such as a sale or a download. Facts are stored in fact tables, and have a foreign key relationship with a number of dimension tables. Dimensions are companions to facts, and describe the objects in a fact table.

What is a junk dimension explain with example?

A Junk Dimension is a dimension table consisting of attributes that do not belong in the fact table or in any of the existing dimension tables. The nature of these attributes is usually text or various flags, e.g. non-generic comments or just simple yes/no or true/false indicators.

What are the 3 types of SCD?

What are the types of SCD?Type 0 – Fixed Dimension. No changes allowed, dimension never changes.Type 1 – No History. Update record directly, there is no record of historical values, only current state.Type 2 – Row Versioning. … Type 3 – Previous Value column. … Type 4 – History Table. … Type 6 – Hybrid SCD.

When would you use a junk dimension?

Junk dimensions are used to reduce the number of dimensions in the dimensional model and reduce the number of columns in the fact table. A junk dimension combines two or more related low cardinality flags into a single dimension.

What are conformed dimensions?

Conformed dimensions are dimensions that are shared by multiple stars. They are used to compare the measures from each star schema [3]. The reuse of conformed dimensions is very common in order to “support true, cross-business process analysis” [6].

Is time a dimension?

“Time is ‘separated’ from space in a sense that time is not a fourth dimension of space. Instead, time as a numerical order of change exists in a 3D space. Our model on space and time is founded on measurement and corresponds better to physical reality.”