In the context of Azure SQL Database and the concept of "Elastic Query," the term "Three and Four-part names" refers to the naming conventions used for referencing objects (tables, views, etc.) across different databases in a federated database system.
- Three-Part Name:
A three-part name includes the name of the database, the schema, and the object name - for example
DatabaseName.dbo.Employee
- Four-Part Name:
A four-part name extends the three-part name by including the server or data warehouse name - for example
ServerName.DatabaseName.dbo.Employee
In Elastic Query, which is part of Azure SQL Database, you can use three and four-part names to query data across multiple databases within the same logical server or even across different logical servers. This is achieved by setting up an elastic database query with the necessary credentials and configurations.
hth
Marcin