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PostgreSQL - COUNT() function example

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Created by:
Amir-Hashempur
337

In this article, we would like to show you how to use COUNT() function in PostgreSQL.

Quick solution:

SELECT COUNT(*) AS "alias_name" FROM "table_name";

Practical example

To show how the COUNT() function works, we will use the following table: 

PostgreSQL - example data used with COUNT() function
PostgreSQL - example data used with COUNT() function

Note:

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

Example

In this example, we will display the number of users.

Query: 

SELECT COUNT(*) AS "number of users" FROM "users";

Output: 

PostgreSQL - COUNT() function result
PostgreSQL - COUNT() function result

Database preparation

create_tables.sql file:

CREATE TABLE "users" (
	"id" SERIAL,
	"name" VARCHAR(50) NOT NULL,
	"surname" VARCHAR(50) NOT NULL,
	"department_id" INTEGER,
    "salary" DECIMAL(15,2) NOT NULL,
	PRIMARY KEY ("id")
);

insert_data.sql file:

INSERT INTO "users"
	( "name", "surname", "department_id", "salary")
VALUES
	('John', 'Stewart', 1, '3512.00'),
	('Chris', 'Brown', 2, '1344.00'),
	('Kate', 'Lewis', 3, '6574.00'),
	('Ailisa', 'Gomez', NULL, '6500.00'),
	('Gwendolyn', 'James', 2, '4200.00'),
	('Simon', 'Collins', 4, '3320.00'),
	('Taylor', 'Martin', 2, '1500.00'),
	('Andrew', 'Thompson', NULL, '2100.00');

PostgreSQL - Functions

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