There is absolutely no reason why a table cannot be used as a dimension table in one data mart and a fact table
Can a table be a fact and dimension?
Additionally, any table in a dimensional database that has a composite key must be a fact table. This means that every table in a dimensional database that expresses a many-to-many relationship is a fact table. Therefore a dimension table can also be a fact table for a separate star schema.
How do you create a fact table and dimension table?
- In Data Modeler, lock the model for editing.
- In the Database menu in the left pane, right-click the source table that contains the fact and dimensional data that you want to model, select Add to Model, and then select Add as Fact and Dimension Tables.
Can you load fact table before dimension?
If you have sales fact table which is loaded first with a record with a sale of $5000. … So, as an order dimensions should be loaded first before the facts. Reason, is to have the related key value (Surrogate Key or the Primary key/Foreign Key) from the dimension (product) to the fact (sales).Can you share dimension tables between fact tables?
It is also possible to share dimension tables between fact tables. For example, time, item, and location dimension tables are shared between the sales and shipping fact table.
What is the relationship between dimension and fact table?
Fact table contains the measuring on the attributes of a dimension table. Dimension table contains the attributes on that truth table calculates the metric. 2. In fact table, There is less attributes than dimension table.
Can a fact be a dimension?
Yes, it can, and sometimes it should, depending on what you are trying to analyze, and how.
What is loading the fact tables and dimension tables?
Fact tables are normally loaded from transaction tables such as order tables or from transactional files, such as web logs. Hence the number of rows to update or insert in a load is much larger than in dimensions. The core of loading fact tables is to change the natural keys into surrogate keys.Why do we need fact and dimension table?
Fact and Dimension tables are the main two tables that are used when designing a data warehouse. The fact table contains measures of columns and surrogate keys that link to the dimension tables. Measure columns are the values that you store in order to measure the business fact.
How do we do the fact load?- Acquire source data.
- Calculate the facts.
- Aggregate the facts to match the grain of the fact table.
- Identify surrogate keys for each of the dimensions.
- Load the new fact table records into the warehouse.
Can we join two fact tables?
The answer for both is “Yes, you can”, but then also “No, you shouldn’t”. Joining fact tables is a big no-no for four main reasons: 1. Fact tables tend to have several keys (FK), and each join scenario will require the use of different keys.
Are fact tables normalized or denormalized?
Fact tables are completely normalized To get the textual information about a transaction (each record in the fact table), you have to join the fact table with the dimension table. Some say that fact table is in denormalized structure as it might contain the duplicate foreign keys.
Can you add a dimension to a fact table once the fact table is established?
There are different types of columns that could be added to a Fact table. You might add a dimension to a Fact table which will be a foreign key relationship to a dimension table; or you might add a measure to a Fact table which will be a numerical value used to perform calculations.
Is it possible to share dimension tables between fact tables True or false?
A fact constellation schema allows dimension tables to be shared between fact tables. For example, the dimensions tables for time, item, and location are shared between the sales and shipping fact tables.
Can star schema have multiple fact tables?
Although the diagram in this chapter shows a single fact table, a star schema can have multiple fact tables. A more complex schema with multiple fact tables is useful when you need to keep separate sets of measurements that share a common set of dimension tables.
When more than one fact table is present in dimensional Modelling then it is called?
A Galaxy Schema contains two fact table that shares dimension tables. It is also called Fact Constellation Schema. Star cluster schema contains attributes of Star and Snowflake Schema.
What is the difference between a fact table and a dimension table?
A fact table works with dimension tables. A fact table holds the data to be analyzed, and a dimension table stores data about the ways in which the data in the fact table can be analyzed. Thus, the fact table consists of two types of columns.
How do you know if it is a fact or a dimension?
Fact table is defined by their grain or its most atomic level whereas Dimension table should be wordy, descriptive, complete, and quality assured. Fact table helps to store report labels whereas Dimension table contains detailed data.
What is the combination of fact and dimension table called?
Keys: Fact table consists of a key that is the combination or concatenation of all primary keys of various dimension tables associated with that fact table. Such key is called a concatenated key which uniquely identifies the row of the fact table.
What are fact and dimension tables with examples?
Example : Time Dimension , Product Dimension. Fact Table : It is nothing but we can maintains information about the metrics or precalculation data. Example : Sales Fact, Order Fact. Star schema : one fact table link with dimension table form as a Start Schema.
What is fact table and what are different types of fact table?
The fact table is a central table in the data schemas. It is found in the centre of a star schema or snowflake schema and surrounded by a dimension table. It contains the facts of a particular business process, such as sales revenue by month.
Which table loaded first fact or dimension?
The process of loading the base schema requires that fact tables and dimension tables be loaded. Fact tables bear foreign keys to the dimension tables and are therefore dependent entities. This would suggest that dimension tables be loaded first.
How do you create a fact table?
To create a Fact table, right click the ‘Fact Tables’ folder (or one of its sub folders) and select Create New. There are two ways to create a Fact Table. By far the quickest way is to import the Meta Data from a Source System, and then edit as required.
How do I join a fact and dimension table in SQL Server?
To create a connection, a line with arrows, between a fact table and a dimension table in the SSMS diagram panel, we specify a primary key for each dimension entity, and assign foreign keys in the fact entities. User-defined data types are used to describe these keys.
How do you populate a fact table?
- Load the facts into a staging table.
- The staging table has additional columns which contain your surrogate keys.
- Run an update statement on your staging table that fills in the surrogate keys.
- Pick an appropriate window in your fact. Delete and reload that window.
How do you populate a dimension table?
Populate the other dimension tables. To do this, you create a Plan for each dimension table with a source Transform, a Key Generation Transform, and a sink Transform. You update a dimension table only when the source data for the dimension table has new or updated records. Populate the fact table.
What is transactional fact table?
A transactional fact table is a fact table where: Each event is stored in the fact table only once. It has a date column indicating when the event occurred. It has an identifier column which identifies each event. The number of rows is the same as the source table.
Can a snowflake schema have more than one fact table?
A schema can have one or more facts, but these facts are not linked by any key relationship. It is best practice not to join fact tables in a single query as you would whey querying a normalized/transactional database.
What are the three types of fact tables?
There are three types of fact tables and entities: Transaction. A transaction fact table or transaction fact entity records one row per transaction. Periodic.
Can we join two fact tables in Obiee?
Joining fact tables is never an ideal solution, but thankfully OBIEE 11g is equipped with the ability to allow us to navigate these situations. Using multiple table sources is a powerful tool, and one that can be leveraged to bring us accurate results for difficult query requests.
Are dimension tables Denormalized?
For dimension tables, you generally model these as one table per object. … Building the dimension in the ETL system involves joining the various normalized description and hierarchy tables that populate the dimension attributes and writing the results into a single table.
