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PostgreSQL - make column values unique

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Created by:
Tehya-Blanchard
304

In this article, we would like to show you how to make column values unique in PostgreSQL.

Quick solution:

ALTER TABLE "table_name" 
ADD UNIQUE ("column_name");

or

ALTER TABLE "table_name"
ADD CONSTRAINT "constraing_name" UNIQUE ("column1", "column2", "columnN");

Practical example

To show how to make column values unique, we will use the following table:

PostgreSQL - example data used to make column values unique
PostgreSQL - example data used to make column values unique

Example 1 - make single column unique

In this example, we will make name column unique.

Query:

ALTER TABLE "users"
ADD CONSTRAINT "UC_username" UNIQUE ("name");

Result:

Using query

SHOW INDEXES FROM "users";
PostgreSQL - make column value unique - result
PostgreSQL - make column value unique - result

Using HeidiSQL

PostgreSQL - make column value unique - result 
PostgreSQL - make column value unique - result

Example 2 - make multiple columns unique

In this example, we will make name and country columns unique.

Query:

ALTER TABLE "users"
ADD CONSTRAINT "UC_user" UNIQUE ("name", "country");

Result:

Using query

SHOW INDEXES FROM "users";
PostgreSQL - make multiple column values unique - result
PostgreSQL - make multiple column values unique - result 

Using HeidiSQL:

PostgreSQL - make multiple column values unique - result
PostgreSQL - make multiple column values unique - result 

PostgreSQL - problems

PostgreSQL - make column values unique
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