USE Database in MySQL

The USE statement tells MySQL which database you want to work with.

USE school;

After this command, school becomes the current database.

The basic syntax is:

USE database_name;

Replace database_name with the name of the database you want to select.

Suppose a database named school already exists.

USE school;

Now SQL statements that do not explicitly specify another database will work with the selected school database.

A common workflow is to create the database first and then select it.

CREATE DATABASE school;

USE school;

The first statement creates the database and the second selects it.

The USE statement does not create a database.

USE school;

The database must already exist and the current user must have appropriate access to it.

Before selecting a database, you can view databases accessible to the current user.

SHOW DATABASES;

Then select the required database.

USE school;

Use the DATABASE() function to check which database is currently selected.

SELECT DATABASE();

For example:

USE school;

SELECT DATABASE();

After selecting the school database, the result can identify the current database:

school

If no database is selected, the result can be NULL.

After selecting a database, you can create tables inside it.

USE school;

CREATE TABLE students (
    id INT PRIMARY KEY,
    name VARCHAR(100)
);

The SHOW TABLES command displays tables from the currently selected database.

USE school;

SHOW TABLES;

Once the database is selected, you can insert records into its tables.

USE school;

INSERT INTO students
(id, name)
VALUES
(1, 'Rahul');

You can retrieve data from a table in the selected database.

USE school;

SELECT * FROM students;

The query reads data from the students table in the school database.

You can change the current database at any time by using another USE statement.

USE school;

USE library;

After the second command, library becomes the current database.

CREATE DATABASE school;
CREATE DATABASE library;

USE school;

SELECT DATABASE();

USE library;

SELECT DATABASE();

This example shows how the current database changes when another database is selected.

The USE statement can be executed in MySQL Workbench's SQL Editor.

USE school;

After executing it, you can work with the tables inside the selected database.

The same statement can be used in the MySQL command-line client.

mysql> USE school;

MySQL will select the database for the current session.

Suppose a library database already exists.

USE library;

You can then work with tables such as:

books
students
issues
returns

For a company application, you could select:

USE company_db;

You could then work with employee, department, and project tables stored in that database.

For a hospital management system:

USE hospital_db;

The selected database can contain tables such as patients, doctors, appointments, and billing.

You do not always have to select a database before referencing a table. You can specify the database name directly.

SELECT *
FROM school.students;

Here, school.students means the students table inside the school database.

The following example demonstrates the relationship between USE and CREATE TABLE.

USE school;

CREATE TABLE teachers (
    id INT PRIMARY KEY,
    name VARCHAR(100),
    subject VARCHAR(100)
);

The teachers table is created in the selected school database.

After selecting the database, you can insert records into its tables.

USE school;

INSERT INTO teachers
(id, name, subject)
VALUES
(1, 'Amit Kumar', 'Mathematics');

You can also update records after selecting the database.

USE school;

UPDATE teachers
SET subject = 'Physics'
WHERE id = 1;

The selected database can also be used for DELETE operations.

USE school;

DELETE FROM teachers
WHERE id = 1;

Always use a suitable WHERE condition when deleting specific records.

If you try to select a database that does not exist, MySQL will report an error.

USE unknown_database;

Make sure the database exists before using the USE statement.

If no database has been selected and you try to perform an operation that requires a current database, MySQL may report that no database is selected.

You can solve this by selecting the required database:

USE school;

A useful workflow is to check the current database before running important queries.

SELECT DATABASE();

USE school;

SELECT DATABASE();

This helps confirm which database is currently active.

Common problems include:

• Database name is incorrect
• Database does not exist
• User does not have access
• Database name is misspelled
• Working with an unexpected database

CREATE DATABASE IF NOT EXISTS school;

SHOW DATABASES;

USE school;

SELECT DATABASE();

CREATE TABLE students (
    id INT PRIMARY KEY,
    name VARCHAR(100),
    course VARCHAR(100)
);

INSERT INTO students
(id, name, course)
VALUES
(1, 'Rahul', 'Python');

SELECT * FROM students;

This example creates a database, selects it, checks the current database, creates a table, inserts data, and retrieves the data.

Suppose you have two databases for different applications:

school_db
library_db

You can switch between them as required:

USE school_db;

SELECT DATABASE();

SHOW TABLES;

USE library_db;

SELECT DATABASE();

SHOW TABLES;

The USE statement makes it easy to switch the working database during a MySQL session.