When we need to improve the performance the first thing comes in your mind is Index, while there are many different things can be done to improve the performance of the system. But indexing of the table should be done carefully which may reduce the query time as unexpected. Although every SQL Server release comes with new updates so we have to know about the index, which one updates comes on Index and which type of index should be used to increase your performance. In this tutorial, we will learn about each type of index available in SQL Server and will explain why/when one could be used to improve the query performance.
In starting I will explain the basic about Index so that new database professional learn about the index in SQL Server.
According to Microsoft Doc, an index is an on-disk structure associated with a table or view that speeds retrieval of rows from the table or view. An index contains keys built from one or more columns in the table or view. These keys are stored in a structure (B-tree) that enables SQL Server to find the row or rows associated with the key values quickly and efficiently.
Type of Index: There are basically two types of index
1- Clustered Indexes
2- Non-Clustered Indexes
But some specialized index types are available in SQL Server, these indexes can create on regular tables and datatypes and some work only on specific datatype, please see the following.
1- ColumnStore Indexes
2- Full-Text Indexes
3- XML Indexes
4- Spatial Indexes
5- Filtered Indexes
Don’t miss one thing which is more important, sometimes index can create trouble if we do not maintain indexes from time to time.
1- Index Fragmentation