Indexing in RDBMS

Index: An index is a special data structure that improves the speed of data retrieval operations on a database table. Think of it as an alphabetical index at the end of a book, which helps you quickly find the page where a specific topic is discussed.

How Indexing Works:

• When you create an index on a database column (or columns), the RDBMS builds a structure that allows it to quickly locate the rows that match a specific query.
• This structure is a hash table that organizes the data in a way that makes searching much faster.

Why Use Indexes?

1. Speed Up Queries: Indexes make searching through large amounts of data much faster. For example, finding all customers whose last name is "Smith" will be quicker if there is an index on the last name column.
2. Efficient Sorting: Indexes can also help with sorting data quickly. For example, sorting orders by date can be much faster if there’s an index on the date column.
3. Improve JOIN Operations: When combining data from multiple tables, indexes can significantly speed up the process.

Example:

Imagine you have a table called students with columns id, name, and grade. You create an index on the name column:

CREATE INDEX idx_name ON students(name);        

Now, if you run a query to find all students named "Alice":

SELECT * FROM students WHERE name = 'Alice';        

The database can use the index to quickly find the rows where the name is "Alice" instead of scanning every row in the table.

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