Indexes

                                              Indexes

• Indexes plays a major role when a data is to be searched in bulk records.
• In indexing a separate index structure is created that includes search key value and address of a record and index always stores the data in ascending order for performing.
• Indexing is classified into the following types

1. Clustered Index
2. Non-Clustered Index
3. Unique Index

Syntax:

Create [Unique]/[Clustered]/[Non-Clustered] Index

index_name ON table_name (column1, column2,........)

Composite Index: Index created on multiple columns is called as Composite index.

1. Clustered Index:

• Clustered index will alter the physical representation of rows in a table(In ascending order).
• A table can have only one clustered index.
• This index should be created for a column where more than one search value is available.

2. Non-Clustered Index:

• It will not allow the physical representation of rows
• It will not sort the data of a table.
• It is a default index created.

3.Unique Index:

• This contains only on those columns which contains unique data.
• This is Automatically created when Unique Constraint is specified on a column.(unique non-clustered)