Table and Index OrganizationTables and indexes are stored as a collection of 8-KB pages. This topic describes the way table and index pages are organized. Table OrganizationThe following illustration shows the organization of a table. A table is contained in one or more partitions and each partition contains data rows in either a heap or a clustered index structure. The pages of the heap or clustered index are managed in one or more allocation units, depending on the column types in the data rows. PartitionsTable and index pages are contained in one or more partitions. A partition is a user-defined unit of data organization. By default, a table or index has only one partition that contains all the table or index pages. The partition resides in a single filegroup. A table or index with a single partition is equivalent to the organizational structure of tables and indexes in earlier versions of SQL Server.When a table or index uses multiple partitions, the data is partitioned horizontally so that groups of rows are mapped into individual partitions, based on a specified column. The partitions can be put on one or more filegroups in the database. The table or index is treated as a single logical entity when queries or updates are performed on the data. For more information, seePartitioned Tables and Indexes.To view the partitions used by a table or index, use thesys.partitions (Transact-SQL)catalog view. Clustered Tables, Heaps, and IndexesSQL Server tables use one of two methods to organize their data pages within a partition:Clustered tables are tables that have a clustered index.The data rows are stored in order based on the clustered index key. The clustered index is implemented as a B-tree index structure that supports fast retrieval of the rows, based on their clustered index key values. The pages in each level of the index, including the data pages in the leaf level, are linked in a doubly-linked list. However, navigation from one level to another is performed by using key values. For more information, seeClustered Index Structures.Heaps are tables that have no clustered index.The data rows are not stored in any particular order, and there is no particular order to the sequence of the data pages. The data pages are not linked in a linked list. For more information, seeHeap Structures.Indexed views have the same storage structure as clustered tables.When a heap or a clustered table has multiple partitions, each partition has a heap or B-tree structure that contains the group of rows for that specific partition. For example, if a clustered table has four partitions, there are four B-trees; one in each partition.Nonclustered Indexes