Clustered vs. Non-Clustered Indexes: Organizing Your Data for Speed in SQL Server

Here's a table summarizing the key differences:

This example creates a table Customers with a clustered index on the CustomerID column. The data in the table will be physically stored sorted by CustomerID.

CREATE TABLE Customers (
  CustomerID int PRIMARY KEY,  -- Primary key enforces uniqueness and automatically creates a clustered index
  CustomerName nvarchar(50) NOT NULL,
  Email nvarchar(100)
);

This example creates a non-clustered index on the Email column of the Customers table. The data will still be physically stored based on the clustered index (CustomerID), but this index will allow for faster searches based on email addresses.

CREATE TABLE Customers (  -- Assuming Customers table already exists
  CustomerID int PRIMARY KEY,
  CustomerName nvarchar(50) NOT NULL,
  Email nvarchar(100) NOT NULL
);

CREATE NONCLUSTERED INDEX IX_CustomerEmail ON Customers(Email);