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PostgreSQL - find duplicated values
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In this article, we would like to show you how to find duplicated values in PostgreSQL.
Quick solution:
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SELECT "column_name", COUNT("column_name")2
FROM "table_name"3
GROUP BY "column_name"4
HAVING COUNT("column_name") > 1;To show how to find duplicated values, 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 names that are duplicated in users table.
Query:
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SELECT "name", COUNT("name") AS "name_number"2
FROM "users"3
GROUP BY "name"4
HAVING COUNT("name") > 1;Result:
create_tables.sql file:
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CREATE TABLE "users" (2
"id" SERIAL PRIMARY KEY,3
"name" VARCHAR(100) NOT NULL,4
"email" VARCHAR(100) NOT NULL,5
"country" VARCHAR(15) NOT NULL6
);insert_data.sql file:
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INSERT INTO "users"2
("name", "email", "country")3
VALUES4
('Tom', 'tom1@email.com', 'Poland'),5
('Tom', 'tom2@email.com', 'Poland'),6
('Tom', 'tom3@email.com', 'Poland'),7
('Kim', 'kim1@email.com', 'Vietnam'),8
('Kim', 'kim2@email.com', 'Vietnam'),9
('Chris', 'chris1@email.com', 'Spain'),10
('Chris', 'chris2@email.com', 'Spain'),11
('Chris', 'chris3@email.com', 'USA');