What is a fact table in a transaction?
Transaction Fact Tables. A given customer or product is likely linked to multiple rows in the fact table because the customer or product is involved in more than one transaction. Transaction data often is structured quite easily into a dimensional framework. The lowest-level data is the most natural dimensional data,...
What is a transaction table?
A Transaction table is the most basic and fundamental view of business operations. These fact tables represent an event that occurred at an instantaneous point in time.
What is the grain of a transaction fact table?
The grain of a transaction fact table is a point in space and time. They hold the smallest of business details. As a transaction happens, extensive context about it is captured. This context creates lots of detail in the dimension tables, so we expect a lot of them.
Why are transaction fact tables dense or sparse?
Transaction fact tables may be dense or sparse because rows exist only if measurements take place. These fact tables always contain a foreign key for each associated dimension, and optionally contain precise time stamps and degenerate dimension keys. The measured numeric facts must be consistent with the transaction grain.
What is transaction fact table?
Transaction Fact Tables A Transaction table is the most basic and fundamental view of business operations. These fact tables represent an event that occurred at an instantaneous point in time. A row exists in the fact table for a given customer or product only if a transaction has occurred.
What is example of fact table?
An example of a fact table. In the schema below, we have a fact table FACT_SALES that has a grain that gives us the number of units sold by date, by store, and product. All other tables such as DIM_DATE , DIM_STORE and DIM_PRODUCT are dimensions tables. This schema is known as the star schema.
What are the 3 types of fact tables?
These are:Transaction fact tables.Periodic snapshot tables, and.Accumulating snapshot tables.
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.
What is a fact table and dimension table example?
A fact table stores quantitative information for analysis and is often denormalized. 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.
What should be in a fact table?
In data warehousing, a fact table consists of the measurements, metrics or facts of a business process. It is located at the center of a star schema or a snowflake schema surrounded by dimension tables.
What is transaction grain?
The transaction grain corresponds to a measurement taken at a single instant. The grocery store beep is a transaction grain. The measured facts are valid only for that instant and for that event. The next measurement event could happen one millisecond later or next month or never.
Can we join 2 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.
How many fact tables are there?
There are four types of fact tables: transaction, periodic snapshot, accumulating snapshot and factless fact tables.
How do you load a fact table?
As stated in Chapter 5, a fact table load must: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.
Do fact tables have primary key?
The fact table also has a primary (composite) key that is a combination of these four foreign keys. As a rule, each foreign key of the fact table must have its counterpart in a dimension table. Additionally, any table in a dimensional database that has a composite key must be a fact table.
What is measure in fact table?
Fact table holds the measures data for measuring the performance of your business. Your business might be sales, purchasing, inventory, logistics, banking, telephony data, and many more.