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PostgreSQL - GROUP BY statement
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In this article, we would like to show you how to use GROUP BY statement in PostgreSQL.
Quick solution:
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SELECT "column1", "column2", "columnN"2
FROM "table_name"3
WHERE condition4
GROUP BY "column_name"5
ORDER BY "column_name";To show how the GROUP BY statement works, we will use the following table:
Note:
At the end of this article you can find database preparation SQL queries.
In this example, we will display the number of users in each country descending.
Query:
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SELECT COUNT("name") AS "number of users", "country"2
FROM "users"3
GROUP BY "country"4
ORDER BY COUNT("name") DESC;Output:
create_tables.sql file:
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CREATE TABLE "users" (2
"id" SERIAL PRIMARY KEY,3
"name" VARCHAR(100) NOT NULL,4
"country" VARCHAR(15) NOT NULL5
);insert_data.sql file:
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INSERT INTO "users"2
("name", "country")3
VALUES4
('Tom', 'Poland'),5
('Chris', 'Spain'),6
('Jack', 'Spain'),7
('Kim', 'Vietnam'),8
('Marco', 'Italy'),9
('Kate', 'Spain'),10
('Nam', 'Vietnam');