DDL and DML Commands in Oracle

 Understanding DDL and DML Commands in DBMS

Database Management Systems (DBMS) play a crucial role in organizing and managing data efficiently. Whether you are a beginner or an aspiring database administrator, understanding SQL commands is essential. SQL commands are categorized into different types, with Data Definition Language (DDL) and Data Manipulation Language (DML) being two of the most fundamental ones.

In this blog post, we will discuss DDL and DML in detail, explore their commands, provide practical SQL examples, and offer downloadable notes along with a homework assignment to reinforce your learning.

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1. What is DDL (Data Definition Language)?

DDL is a set of SQL commands used to define and modify the structure of a database. These commands affect the schema, such as creating or altering
tables, but do not manipulate the data within them. DDL commands are auto-committed, meaning they are executed permanently without the need for an explicit commit.

Common DDL Commands:

• CREATE: Used to create a new database or table.

  CREATE TABLE Students (
      ID INT PRIMARY KEY,
      Name VARCHAR(50),
      Age INT
  );

• ALTER: Modifies an existing table structure.

  ALTER TABLE Students ADD COLUMN Email VARCHAR(100);

• DROP: Deletes a table and its data permanently.

  DROP TABLE Students;

• TRUNCATE: Removes all records from a table but keeps its structure.

  TRUNCATE TABLE Students;

DDL commands are essential for database administrators and developers to define a structured database efficiently.

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2. What is DML (Data Manipulation Language)?

DML commands are used to manipulate and retrieve data from existing tables. Unlike DDL, these commands focus on modifying data without altering the database structure. DML commands are not auto-committed, meaning changes can be rolled back if needed.

Common DML Commands:

• INSERT: Adds new records to a table.

  INSERT INTO Students (ID, Name, Age) VALUES (1, 'Rahul', 20);

• UPDATE: Modifies existing records based on conditions.

  UPDATE Students SET Age = 21 WHERE ID = 1;

• DELETE: Removes specific records from a table.

  DELETE FROM Students WHERE ID = 1;

• SELECT: Retrieves data from a table.

  SELECT * FROM Students;

DML commands are crucial for day-to-day database operations, as they allow users to interact with stored data effectively.

Download PDF Notes and Homework