Data Manipulation Language (DML)

Data Manipulation Language (DML) is used in SQL (Structured Query Language) to perform operations that modify or manage the data in a database. It includes INSERT, UPDATE, and DELETE commands. Let’s go through these commands in a simple, beginner-friendly way with real-life examples.

1. INSERT Command

The INSERT command is used to add new records (rows) to a table in the database.

Syntax:

INSERT INTO table_name (column1, column2, ...) VALUES (value1, value2, ...);

    

Example:

Imagine you have a table called Students with the following structure. You want to add a student record to the table.

INSERT INTO Students (StudentID, Name, Age, Grade)
VALUES (1, 'John Doe', 18, 'A');

    

After executing this command, the Students table will look like this:

2. UPDATE Command

The UPDATE command is used to modify existing records in a table.

Syntax:

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

    

Example:

Let's say John Doe's grade needs to be updated from 'A' to 'B'.

UPDATE Students
SET Grade = 'B'
WHERE StudentID = 1;

    

After executing this command, the Students table will look like this:

3. DELETE Command

The DELETE command is used to remove existing records from a table.

Syntax:

DELETE FROM table_name
WHERE condition;

    

Example:

If you need to remove John Doe's record from the Students table.

DELETE FROM Students
WHERE StudentID = 1;

    

After executing this command, the Students table will be empty.

Key Points to Remember

• INSERT: Adds new rows to a table.
• UPDATE: Modifies existing rows based on a condition.
• DELETE: Removes rows based on a condition.

Practical Real-World Example

If you’re managing a library database:

• Use INSERT to add details of a new book.
• Use UPDATE to change the availability status of a borrowed book.
• Use DELETE to remove records of outdated or damaged books.