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What is the need of surrogate key?
Surrogate Keys. A surrogate key is a unique key for an entity in the client’s business or for an object in the database. Sometimes natural keys cannot be used to create a unique primary key of the table. This is when the data modeler or architect decides to use surrogate or helping keys for a table in the LDM.
What is surrogate key in dimension table?
A surrogate key uniquely identifies each entity in the dimension table, regardless of its natural source key. This is primarily because a surrogate key generates a simple integer value for every new entity. Surrogate keys are necessary to handle changes in dimension table attributes.
Can a 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. Therefore a dimension table can also be a fact table for a separate star schema.
When to use a surrogate key for a dimension table?
Meaningless integer keys, otherwise known as surrogate keys, are commonly used as primary keys for dimension tables in data warehouse designs. Our students frequently ask us – what about fact tables? Should a unique surrogate key be assigned for every row in a fact table?
Is a surrogate primary key needed on a fact table in a?
You should at least have a natural key on the fact table so you can identify rows and reconcile them against source or track changes where this is necessary. On SQL Server an identity column gives you a surrogate key for free and on other systems using sequences (e.g. Oracle) it can be added fairly easily.
When does a surrogate key become a business key?
As soon as the business uses the surrogate key to uniquely identify (and track) data in the source system, the surrogate key becomes a business key. We have taught students of computer science to use surrogate keys as primary keys in database development because it can speed up joins between tables.
How are surrogate keys different from natural keys?
1. Surrogate keys do not change while the row exists. 2. Natural keys might change in the source (e.g., migration to a new system), making them useless in the data warehouse. 3. Surrogate keys have numeric data types, which provide excellent performance during data processing and business queries.