Types Of Indexes in SQL

Discuss Types of Database Indexes

Utilize Real-Life Examples.

Single-Column Index

This is the most basic of indexes. We use it to index a single column. Think of it like a textbook's index at the back. You need one when looking for specific information. It is an arrangement of keywords.

Example:

Consider a database table. It holds a large group of books. Each book has individual pages. You have a list of ISBN numbers. You want to find the books. You can use a single-column index for this. It is as if each ISBN number is a page in the book index.

Visualize a library. Books get arranged by the author's last name. They work as a fast technique. It helps in finding all books by one author.

Example: It's simple to find all books by "J.K. Rowling". This is possible as they group together in the library.

CREATE INDEX author_index ON books (author);

    

Composite Index (Multi-Column Index)

These are more advanced. They are similar to the index of a professional journal. Such an index lists articles under multiple topics. They give a combined path to specific articles.

Example:

Imagine a movie database. It contains a number of genres. It also has a list of release dates. Viewing trend reports is your objective. By using a composite index, you save time. You jump over long lists. The index combines both genre and date of release. This process mirrors the activity of studying academic research.

Let's think of a recipe book. This book organizes recipes using the main ingredient plus the cooking method. This helps to find recipes quickly. You can find those that use specific ingredients and methods together.

Example: The book easily presents recipes for "Chicken Grilling". The organization of the book causes this. The book groups together recipes by both "Chicken" and "Grilling".

CREATE INDEX ingredient_method_index ON recipes (main_ingredient, cooking_method);

    

Unique Index

Unique Index ensures that all values in a column are distinct. It guarantees that no duplicate values are stored in the indexed column.

Example:

Imagine unique ID numbers for people. This is what we can compare to. Uniqueness is vital. No two individuals can hold the same ID. This system provides a guarantee. Each person has individuality.

Consider unique social security numbers. Each individual has an exclusive number linked to them. This measure prevents identical IDs for two people.

CREATE UNIQUE INDEX ssn_index ON workers (ssn);

    

Clustered Index (Primary Index)

A Clustered Index determines the physical order of data in the table. It organizes rows by the key value. It is like sorting books in a library by subject.

Example:

Envision books in a library. They're sorted by subject. All books on a topic group together on the shelf.

Example: Books about "History" are in one part of the library. They're together physically.

CREATE CLUSTERED INDEX order_id_index ON orders (order_id);

    

Non-Clustered Index

A Non-Clustered Index does not alter the physical order of the table. It creates a separate structure that points to the data.

Example:

Think of a cookbook index. It sits at the back. It lists recipes by ingredients. It's a help to find the recipe. It doesn't change the order of recipes.

Example: The index allows you to find recipes that use "Tomatoes". The cookbook's recipe order does not get reshuffled.

CREATE NONCLUSTERED INDEX ingredient_index ON cookbook (ingredient);

    

Conclusion

Put plainly, indexes are akin to specialized listings. They resemble arrangements. They quicken the quest for items in a large group. Just think of how a library or cookbook operates. Each utilizes diverse techniques to aid. They assist in finding books. They help to find recipes more easily.