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PostgreSQL - add index to existing table
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In this article, we would like to show you how to add index to an existing table in PostgreSQL.
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" SERIAL,
"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');