Clustered indexes are the cornerstone of good database
design. A poorly-chosen clustered index doesn't just lead to high
execution times; it has a 'waterfall effect' on the entire system,
causing wasted disk space, poor IO, heavy fragmentation, and more.
As a guideline, clustered Indexes should be Narrow, Unique, Static and Ever Increasing (NUSE). Michelle Ufford Explains why...
www.simple-talk.com/sql/learn-sql-server
A clustered index determines the physical order of data in a table. A clustered index is analogous to a telephone directory, which arranges data by last name. Because the clustered index dictates the physical storage order of the data in the table, a table can contain only one clustered index. However, the index can comprise multiple columns (a composite index), like the way a telephone directory is organized by last name and first name....
A nonclustered index is analogous to an index in a textbook. The data is stored in one place, the index in another, with pointers to the storage location of the data. The items in the index are stored in the order of the index key values, but the information in the table is stored in a different order (which can be dictated by a clustered index). If no clustered index is created on the table, the rows are not guaranteed to be in any particular order....
As a guideline, clustered Indexes should be Narrow, Unique, Static and Ever Increasing (NUSE). Michelle Ufford Explains why...
www.simple-talk.com/sql/learn-sql-server
A clustered index determines the physical order of data in a table. A clustered index is analogous to a telephone directory, which arranges data by last name. Because the clustered index dictates the physical storage order of the data in the table, a table can contain only one clustered index. However, the index can comprise multiple columns (a composite index), like the way a telephone directory is organized by last name and first name....
A nonclustered index is analogous to an index in a textbook. The data is stored in one place, the index in another, with pointers to the storage location of the data. The items in the index are stored in the order of the index key values, but the information in the table is stored in a different order (which can be dictated by a clustered index). If no clustered index is created on the table, the rows are not guaranteed to be in any particular order....
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