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    To create a table with a primary key in MySQL, you can use the CREATE TABLE statement. A primary key uniquely identifies each record in the table and ensures that no duplicate or NULL values are present in the specified column(s).

    Example: Single-Column Primary Key

    CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    PRIMARY KEY (ID)
    );
    Copié !

    In this example, the ID column is defined as the primary key.

    Example: Multi-Column Primary Key

    CREATE TABLE Orders (
    OrderID int NOT NULL,
    ProductID int NOT NULL,
    OrderDate date,
    PRIMARY KEY (OrderID, ProductID)
    );
    Copié !

    Here, the combination of OrderID and ProductID forms the primary key.

    Adding a Primary Key to an Existing Table

    If you need to add a primary key to an existing table, you can use the ALTER TABLE statement:

    ALTER TABLE Persons
    ADD PRIMARY KEY (ID);
    Copié !

    This command adds a primary key to the ID column of the Persons table.

    Removing a Primary Key

    To remove a primary key from a table, use the following SQL statement:

    ALTER TABLE Persons
    DROP PRIMARY KEY;
    Copié !
    How do I add a primary key to a table?
    To add a primary key to an existing table, use the ALTER TABLE statement, replacing the placeholder values with your own: ALTER TABLE your_table_name ADD PRIMARY KEY (column1, column2, ...); For example, the command below combines a customer ID column with a customer last name column to create a primary key in a table named car.
    docs.digitalocean.com
    GeeksForGeeks
    https://www.geeksforgeeks.org/mysql/mysql-primary-key
    MySQL Primary Key - GeeksforGeeks
  1. W3School
    https://www.w3schools.com › mysql › mysql_primaryk…Traduire ce résultat

    MySQL PRIMARY KEY Constraint - W3Schools

    The PRIMARY KEYconstraint uniquely identifies each record in a table. Primary keys must contain UNIQUE values, and cannot contain NULL values. A table can have only O…
    Primary Key on Create Table

    The following SQL creates a PRIMARY KEYon the "ID" column when the "Persons" table is created: To allow naming of a PRIMARY KEY constraint, and for defining a PRIMARY KEYconstraint on multiple columns, use the following SQL syntax: N…

    Primary Key on Alter Table

    To create a PRIMARY KEYconstraint on the "ID" column when the table is already created, use the following SQL: To allow naming of a PRIMARY KEY constraint, and for defining a PRIMARY KEYconstraint on multiple columns, use the following SQL s…

  2. GeeksForGeeks
    https://www.geeksforgeeks.org › my…Traduire ce résultat

    MySQL Primary Key - GeeksforGeeks

    23 juil. 2025 · A table can only have one primary key, but it can be defined on one or more fields and that is called a composite primary key. We can use the …

  3. MySQL
    https://dev.mysql.com › ... › en › create-table.htmlTraduire ce résultat

    MySQL :: MySQL 8.4 Reference Manual :: 15.1.20 CREATE TABLE …

    If you do not have a PRIMARY KEY and an application asks for the PRIMARY KEY in your tables, MySQL returns the first UNIQUE index that has no NULL columns as the PRIMARY KEY.

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  5. Stack Overflow
    https://stackoverflow.com › questionsTraduire ce résultat

    PRIMARY KEY definition in MySQL CREATE TABLE statement

    5 juin 2015 · MySQL allows uses the PRIMARY KEY directive to allow you to set the Primary Key dynamically. Supplying PRIMARY KEY as an argument to the constructor can only be called on …

    • Avis : 2
    • Devart Blog
      https://blog.devart.com › mysql-primary-key-create...Traduire ce résultat

      MySQL Primary Key Guide: CREATE TABLE and ALTER TABLE …

      • Afficher plus

      6 janv. 2025 · Learn how to define and modify primary keys in MySQL using CREATE TABLE and ALTER TABLE statements. See examples and best practices for maintaining data integrity.

    • DigitalOcean
      https://docs.digitalocean.com › ... › create-primary-keysTraduire ce résultat

      How to Create Primary Keys for MySQL Database Tables

      27 mai 2021 · Create primary keys to increase search accuracy, performance, and ensure reliable data replication.

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    • SQL.sh
      https://sql.sh › cours › create-table › primary-key

      SQL PRIMARY KEY

      Dans le langage SQL la “PRIMARY KEY”, autrement la clé primaire, permet d’identifier chaque enregistrement dans une table de base de données. Chaque enregistrement de cette clé primaire doit …

    • TechOnTheNet
      https://www.techonthenet.com › mysql › primary_keys.…Traduire ce résultat

      MySQL: Primary Keys - TechOnTheNet

      This MySQL tutorial explains how to create and drop a primary key in MySQL with syntax and examples. In MySQL, a primary key is a single field or combination of fields that uniquely defines a record.

    • DataCamp
      https://www.datacamp.com › doc › mysql › mysql-prim…Traduire ce résultat

      MySQL PRIMARY KEY Indexes: Usage & Examples - DataCamp

      Learn how to use the MySQL PRIMARY KEY to ensure unique, non-null values in your database tables, enhancing data integrity and optimizing performance with practical examples and best practices.

    • MySQL Tutorial
      https://www.mysqltutorial.org › ... › mysql-primary-keyTraduire ce résultat

      MySQL Primary Key

      In this tutorial, you will learn how to use MySQL primary key constraint to create the primary key for a table.

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