Indexing in database

Question

Diffrence Between Clusterd index and Non clusterd index in depth

Rajeesh Menoth · Answer

Hi, Clustered Index Only one per table Faster to read than non clustered as data is physically stored in index order Non Clustered Index Can be used many times per table Quicker for insert and update operations than a clustered index Reference : http://www.c-sharpcorner.com/blogs/differences-between-clustered-index-and-nonclustered-index1 https://msdn.microsoft.com/en-IN/library/ms190457.aspx

Saddam Mohd · Answer

hi lalit Clustered Clustered indexes sort and store the data rows in the table or view based on their key values. These are the columns included in the index definition. There can be only one clustered index per table, because the data rows themselves can be sorted in only one order. The only time the data rows in a table are stored in sorted order is when the table contains a clustered index. When a table has a clustered index, the table is called a clustered table. If a table has no clustered index, its data rows are stored in an unordered structure called a heap. Nonclustered Nonclustered indexes have a structure separate from the data rows. A nonclustered index contains the nonclustered index key values and each key value entry has a pointer to the data row that contains the key value. The pointer from an index row in a nonclustered index to a data row is called a row locator. The structure of the row locator depends on whether the data pages are stored in a heap or a clustered table. For a heap, a row locator is a pointer to the row. For a clustered table, the row locator is the clustered index key. Reference... https://msdn.microsoft.com/en-IN/library/ms190457.aspx

Vineet Kumar · Answer

Please visit the below link for detailed information : https://www.simple-talk.com/sql/performance/14-sql-server-indexing-questions-you-were-too-shy-to-ask/

Daniel Jones · Answer

Clustered Index Only one clustered index can be there in a table Usually made on the primary key. Sort the records and store them physically according to the order The leaf nodes of a clustered index contain the data pages. Data retrieval is faster than non-clustered indexes Non-Clustered Index There can be any number of non-clustered indexes in a table Usually made on the any key. Do not affect the physical order. Create a logical order for data rows and use pointers to physical data files The leaf node of a nonclustered index does not consist of the data pages. Instead, the leaf nodes contain index rows. Data insertion/update is faster than clustered index For more information visit: http://www.sqlserverlogexplorer.com/overview-of-cluster-and-noncluster-index/

Munesh Sharma · Answer

Clustered Index Only one per table Faster to read than non clustered as data is physically stored in index order Non Clustered Index Can be used many times per table Quicker for insert and update operations than a clustered index Both types of index will improve performance when select data with fields that use the index but will slow down update and insert operations. Because of the slower insert and update clustered indexes should be set on a field that is normally incremental ie Id or Timestamp. SQL Server will normally only use an index if its selectivity is above 95%.