Clustered table???

Clustered table
A clustered table provides an optional method for storing table data. A cluster is made up of a table or group of tables that share the same data blocks, which are grouped together because they share common columns and are often used together.

Clusters have the following characteristics:

· Clusters have a cluster key, which is used to identify the rows that need to be stored together.

· The cluster key can consist of one or more columns.

· Tables in a cluster have columns that correspond to the cluster key.

· Clustering is a mechanism that is transparent to the applications using the tables. Data in a clustered table can be manipulated as though it were stored in a regular table.

· Updating one of the columns in the cluster key may migrate the row.

· The cluster key is independent of the primary key. The tables in a cluster can have a primary key, which may be the cluster key or a different set of columns.

· Clusters are usually created to improve performance. Random access to clustered data may be faster, but full table scans on clustered tables are generally slower.

· Clusters renormalize the physical storage of tables without affecting the logical structure.