A cluster is a schema object that contains data from one or more tables, which have one or more columns in common. Oracle Database stores together all the rows from all the tables that share the same cluster key.
PowerDesigner models clusters as extended objects with a stereotype of <<Cluster>>.
You can modify an object's properties from its property sheet. To open a cluster property sheet, double-click its Browser in the Clusters folder.
The following extended attributes are available on the General tab:
In addition, the following tabs are available:
Columns – lists the columns associated with the cluster. You can can define the following extended attributes for cluster columns:
Name |
Description |
---|---|
Data type |
Specifies the data type for the cluster index. Scripting name: Datatype |
Length |
Specifies the length for the cluster index. Scripting name: DatatypeLength |
Precision |
Specifies the precision for the cluster index. Scripting name: DatatypePrec |
Sort |
This clause instructs Oracle Database to sort the rows of the cluster on this column before applying the hash function. Scripting name: RowSort |
Name |
Description |
---|---|
Owner |
Specifies the owner of the cluster index Scripting name: Owner |
Unique |
Specifies whether the cluster index is unique. Scripting name: Unique |
Bitmap |
Specifies if the index is to be created with a bitmap for each distinct key, rather than indexing each row separately. Scripting name: Bitmap |
Sort |
By default, Oracle Database sorts indexes in ascending order when it creates the index. You can specify NOSORT to indicate to the database that the rows are already stored in the database in ascending order, so that Oracle Database does not have to sort the rows when creating the index. Scripting name: Sort |