MS SQL Server - add index to existing table

TODO: indexy na koniec 

In this article, we would like to show you how to add index to an existing table in MS SQL Server.

Quick solution:

CREATE INDEX [index_name]
ON [table_name] ([column1], [column2], [columnN]);

or

ALTER TABLE [table_name] 
ADD INDEX [index_name] ([column2], [column2], [columnN]);

Practical example

To show how to add index to existing table, we will use the following table:

Note:

At the end of this article you can find database preparation SQL queries.

Example 1 - one column index

In this example, we will create an index for the salary column in users table.

Query:

CREATE INDEX [salary_index]
ON [users] ([salary]);

Result:

1. Using query

SHOW INDEX FROM [users] FROM [dirask];    -- where users-table_name, dirask-database_name

2. Using HeidiSQL

Example 2 - two column index

In this example, we will create an index on the name and surname columns in users table.

Query:

CREATE INDEX [full_name_index]
ON [users] ([name], [surname]);

Result:

1. Using query

SHOW INDEX FROM [users] FROM [dirask];    -- where users-table_name, dirask-database_name

2. Using HeidiSQL

Example 3 - using ALTER TABLE

In this example, we will create an index on two columns using ALTER TABLE statement.

Query:

ALTER TABLE [users] 
ADD INDEX [index_full_name] ([name], [surname]);

Result:

1. Using query

SHOW INDEX FROM [users] FROM [dirask];    -- where users-table_name, dirask-database_name

2. Using HeidiSQL

Database preparation

create_tables.sql file:

CREATE TABLE [users] (
	[id] INT IDENTITY(1,1),
	[name] VARCHAR(50) NOT NULL,
	[surname] VARCHAR(50) NOT NULL,
    [salary] DECIMAL(15,2) NOT NULL,
	PRIMARY KEY ([id])
);

insert_data.sql file:

INSERT INTO [users]
	( [name], [surname], [salary])
VALUES
	('John', 'Stewart', '3512.00'),
	('Chris', 'Brown', '1344.00'),
	('Kate', 'Lewis', '6574.00'),
	('Ailisa', 'Gomez', '6500.00'),
	('Gwendolyn', 'James', '4200.00'),
	('Simon', 'Collins', '3320.00'),
	('Taylor', 'Martin', '1500.00'),
	('Andrew', 'Thompson', '2100.00');