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SQL Server uses binary tree with intermediate and leaf node for search but how it will do this. Ex. If a table employee has two fields
Id bigint
Name varchar(50)
with values such as
Id Name
1 Ashish
2 Amit
3 Bhavin
4 Dinesh
If we have created composite non-clustered index on both of this columns with name as first and Id after this than how it work. Whether intermediate nodes contain 1) A-F 2)G-M ... or something else. Also once name is searched in binary then after this tree has id has intermediate node.
In short how does SQL server search in this type of conditions?
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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. SQL Server documentation uses the term B-tree generally in reference to indexes.
Indexing is the way to get an unordered table into an order that will maximize the query's efficiency while searching. When a table is unindexed, the order of the rows will likely not be discernible by the query as optimized in any way, and your query will therefore have to search through the rows linearly.
Indexes are created using a few database columns. The first column is the Search key that contains a copy of the primary key or candidate key of the table. These values are stored in sorted order so that the corresponding data can be accessed quickly. Note: The data may or may not be stored in sorted order.
Why Indexing is used in database? Answer: An index is a schema object that contains an entry for each value that appears in the indexed column(s) of the table or cluster and provides direct, fast access to rows. The users cannot see the indexes, they are just used to speed up searches/queries.
How It Works
The database takes the columns specified in a CREATE INDEX command and sorts the values into a special data structure known as a B-tree. A B-tree structure supports fast searches with a minimum amount of disk reads, allowing the database engine to quickly find the starting and stopping points for the query we are using.
For more info, check THIS!
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