|
Posted On:
27/09/2012 11:38:24
|
Indexes in databases are similar to indexes in books. In a database, an index allows the database program tofind data in a table without scanning the entire table. An index in a database is a list of values in a table with the storage locations of rows in the table that contain each value.
Indexes can be created on either a single column or a combination of columns in a table and are implemented in the form of B-trees.
An index contains an entry with one or more columns (the search key) from each row in a table. A B-tree is sorted on the search key, and can be searched efficiently on any leading subset of the search key.
For example, an index on columns A, B, C can be searched efficiently on A, on A, B, and A, B, C.
|
|
|
|