Setting Primary Key in Database Tables

1 year ago
Benjamin Taylor
1 minute

When creating database tables, you can set primary keys in the following ways:

  1. To use a primary key constraint, when creating a table, you can add a PRIMARY KEY constraint after the column that needs to be designated as the primary key. For example:
CREATE TABLE employees (
    employee_id INT PRIMARY KEY,
    first_name VARCHAR(50),
    last_name VARCHAR(50)
);
  1. We can use auto-increment primary keys by using the AUTO_INCREMENT or SERIAL keyword to let the database generate primary key values automatically. For example:
CREATE TABLE employees (
    employee_id INT AUTO_INCREMENT PRIMARY KEY,
    first_name VARCHAR(50),
    last_name VARCHAR(50)
);
  1. Using composite keys: multiple columns can be combined to form a primary key. For example:
CREATE TABLE employees (
    employee_id INT,
    department_id INT,
    PRIMARY KEY (employee_id, department_id)
);

No matter which way you choose to set the primary key, you can ensure the uniqueness of each row of data in the table and improve the efficiency of data retrieval.

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