What are dimensions and fact tables?
Difference between Fact Table and Dimension Table
| Fact Table | Dimension Table |
|---|---|
| A fact table is arranged vertically. | The dimension table, on the other hand, is a horizontal table. |
| A fact table can have both numerical and text attribute formats. | A dimension table’s attribute format is text. |
What is facts and dimension with example?
Facts tables could contain information like sales against a set of dimensions like Product and Date. Evert dimension table contains attributes which describe the details of the dimension. E.g., Product dimensions can contain Product ID, Product Category, etc.
What is dimension table and fact table in Hana?
The fact table contains measure values and primary key for Dimension tables. Dim tables contain master data. Fact and dimension table are joined in HANA Modeling to achieve some business logic. Example of Measures − Number of unit sold, Total Price, Average Delay time, etc.
What is the relationship between facts and dimensions?
In most dimensions, each fact joins to one and only one dimension member, and a single dimension member can be associated with multiple facts. In relational database terminology, this is referred to as a one-to-many relationship. However, it is frequently useful to join a single fact to multiple dimension members.
What are the 3 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.
Is fact table is Normalised?
Fact tables are always Normalized. Where as dimension tables are may be normalized or denormalized.In Star schema, Fact table is normalized and Dimension table may be normalized or Denormalized.In Snowflake schema, the Fact table is normalized and Dimension tables are always normalized.
Why do we use facts and dimensions?
basically, our data warehouse implements dimensional modeling or I can say dimensional modeling is a technique used to design the data warehouse where facts and dimensions are used to store the data.
What is fact table example?
A Fact Table is one that holds the primary keys of the referenced dimension tables along with some quantitative metrics (i.e. measurements) over which some sort of calculation can be performed. Some common examples of facts tables include orders, logs and time-series financial data.
What are the types of fact tables?
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.
What is fact and dimension in ETL?
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.
Can fact table have NULL values?
Null-valued measurements behave gracefully in fact tables. The aggregate functions (SUM, COUNT, MIN, MAX, and AVG) all do the “right thing” with null facts. However, nulls must be avoided in the fact table’s foreign keys because these nulls would automatically cause a referential integrity violation.
Can you 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.
What are the four 4 types of database normalization?
First Normal Form (1 NF) Second Normal Form (2 NF) Third Normal Form (3 NF) Boyce Codd Normal Form or Fourth Normal Form ( BCNF or 4 NF)
Can a fact table also be a 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.
Can fact table have duplicates?
Key with multiple columns
Example of records in the table F_Sales: Using once again our multidimensional example model, the query to search for duplicates in the fact table is the following: The query should return 0 results. Same as before, if it returns any record, it represents a duplicate.
What are three types of facts?
We can divide the Facts in to these three types.
- Non-Additive.
- Semi-Additive.
- Additive.
Can two fact tables be joined?
Does fact table 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.
Can a table be both fact and dimension?
Can fact table have foreign key?
What is 1NF 2NF 3NF?
A relation is in 1NF if it contains an atomic value. 2NF. A relation will be in 2NF if it is in 1NF and all non-key attributes are fully functional dependent on the primary key. 3NF. A relation will be in 3NF if it is in 2NF and no transition dependency exists.
How do you convert 1NF to 3NF?
To normalize a table from 1NF to 3NF, you need to normalize it to 2NF first then to 3NF. In the normalization process, you decompose a table into multiple tables that contain the same information as the original table. The normalization process usually removes many problems related to data modification.
Can fact table have primary key?
Can two dimensional tables join?
Apart from this , theoratically we can join any two dimension tables when there is 1 : 1 or 1:n join between them, only when there is n:n joins then you should be careful . you can add customer key and customerid in the address dimension table.