To use a database in MySQL, you need to select it as the active database for your current session. Once a database is selected, all subsequent queries (such as SELECT, INSERT, UPDATE, DELETE, etc.) will be executed on the tables within that database.

Steps to Use a Database in MySQL

1. Open the MySQL Command-Line Client

First, log in to the MySQL server using the MySQL command-line client or a MySQL GUI tool like MySQL Workbench.

mysql -u username -p

• -u username: Your MySQL username.
• -p: Prompts for your password.

2. View Available Databases

To see a list of all available databases on your MySQL server, use:

SHOW DATABASES;

This will display all the databases you have access to.

3. Select the Database You Want to Use

To use a specific database, you need to select it with the USE statement:

USE database_name;

• database_name: The name of the database you want to use.

For example, if you want to use a database named company_db, you would execute:

USE company_db;

4. Verify the Current Database

To confirm which database is currently in use, you can run:

SELECT DATABASE();

This will return the name of the database you are currently using.

5. Start Performing Operations on the Database

Once the database is selected, you can perform any operations on it, such as creating tables, inserting data, querying data, etc.

• Creating a Table:

  CREATE TABLE employees (
      id INT AUTO_INCREMENT PRIMARY KEY,
      name VARCHAR(100),
      position VARCHAR(100),
      salary DECIMAL(10, 2)
  );
  

• Inserting Data:

  INSERT INTO employees (name, position, salary)
  VALUES ('John Doe', 'Manager', 75000.00);
  

• Querying Data:

  SELECT * FROM employees;
  

• Updating Data:

  UPDATE employees
  SET salary = 80000.00
  WHERE name = 'John Doe';
  

• Deleting Data:

  DELETE FROM employees
  WHERE name = 'John Doe';
  

Important Considerations

• Multiple Databases: If you have multiple databases and you want to switch between them, simply use the USE command again with the name of the new database.
• Privileges: Ensure that your MySQL user has the necessary privileges to perform operations on the selected database.

Example Session

Here's an example of a complete session:

SHOW DATABASES;
-- List all databases

USE company_db;
-- Select the `company_db` database

SELECT DATABASE();
-- Verify that `company_db` is the current database

CREATE TABLE departments (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(100),
    location VARCHAR(100)
);
-- Create a new table in the `company_db` database

INSERT INTO departments (name, location)
VALUES ('HR', 'New York'), ('Sales', 'Los Angeles');
-- Insert data into the `departments` table

SELECT * FROM departments;
-- Query data from the `departments` table