Database languages are specialized programming languages that are used to communicate with and manipulate databases. There are two main categories of database languages: data definition languages (DDL) and data manipulation languages (DML).
In other words, a database language is a programming language that is used to create, modify and maintain the structure and content of a database. There are two main types of database languages: Data Definition Language (DDL) and Data Manipulation Language (DML).
Data Definition Language (DDL)
DDL is a set of commands that are used to define the database schema. It is used to create, modify, and delete database objects such as tables, indices and users. This includes specifying the structure of the database, as well as any constraints or rules that should be enforced on the data. Examples of DDL commands include
- CREATE: – To create objects in the database.
- ALTER: – To change the structure of the database.
- DROP: – to delete objects from the database.
Data Manipulation Language (DML)
DML is a set of commands that are used to manipulate the data stored in a database. It is used to insert, update, delete, and retrieve data from the database. This includes operations such as inserting, updating, and deleting data. Examples of DML commands include
- SELECT: – Retrieve data from a database.
- INSERT: – Insert data in a table.
- UPDATE: – To update the existing data in the table.
- DELETE: – To delete all the records from the table.
For example, the following SQL statements are examples of DDL and DML commands:
CREATE TABLE users ( user_id INT PRIMARY KEY, username VARCHAR(255) NOT NULL, password VARCHAR(255) NOT NULL); ALTER TABLE users ADD security_question VARCHAR(255); DROP TABLE users;
INSERT INTO users (user_id, username, password) VALUES (5, 'jane', 'password123'); UPDATE users SET password = 'newpassword' WHERE user_id = 1; DELETE FROM users WHERE user_id = 5;
Both DDL and DML are essential parts of working with databases, and they are often used together in order to create a functional database system.