Opaque View (select Table) And Alias

Opaque View(Select Table) And Alias:

1. What are opaque views in database? When is it advisable to create one?

1. The opaque views are tables that are created with join or other query data that contain “SELECT” query output. The opaque views make the logical understanding simple for implementation but there are heavy performance constraints. They are only used when there is no other way to get to the final solution.

2.What is the purpose of Alias Table?

A) An Alias table (Alias) is a physical table with the type of Alias. It is a reference to a logical table source, and inherits all its column definitions and some properties from the logical table source. A logical table source shows how the logical objects are mapped to the physical layer and can be mapped to physical tables, stored procedures, and select statements. An alias table can be a reference to any of these logical table source types.

a. Alias Tables can be an important part of designing a physical layer. The following is a list of the main reasons to create an alias table.

b.” To reuse an existing table more than once in your physical layer (without having to import it several times).

c. ” To set up multiple alias tables, each with different keys, names, or joins.

d. To help you design sophisticated star or snowflake structures in the business model layer.

e. Alias tables are critical in the process of converting ER Schemas to Dimensional Schemas.

2.  Advantages of Alias table?

A) Alias is useful to rename physical layer objects.

a. Creating self joins.

b. Avoiding closed paths.