First page Back Continue Last page Graphics


Notes:

Creating Updatable View Objects (continued)

Selected in Query: When selected for a transient attribute, this attribute appears in the view object’s SELECT statement. SQL-derived attributes always appear in the view object’s SELECT statement.

Discriminator: Select if this is a discriminator column for a polymorphic view object; this type of view object is discussed in the course Build Applications with ADF II.

Key Attribute: When selected, this attribute forms part of the view object’s key. Entity attributes defined as primary keys will automatically be selected as a Key Attribute when view objects based on the entity are created. You may need to modify this property for view objects based on more than one entity object, where multiple primary keys are defined.

Queryable: Selected if this attribute can occur in a view object's WHERE clause. It is selected by default except for LOBs. This option cannot be selected for LOBs.

Effective Date: It is available only for view attributes that are based on entity attributes for which the effective date is defined. The attribute is either the start or end date of a date range for which the view row is effective (used for a point of time snapshot to answer such questions as what an employee’s salary was on January 30, 2004.)

Updatable: You can enable the attribute to always or never be updatable, or enable it to be updated only before the underlying entity is first posted (while new).

Query Column

Alias: Aliases are optional, but can be useful in SQL-derived attributes to prevent naming conflicts.

Type: This defines the SQL data type of the query column

Expression: An expression is required for a SQL-derived attribute.