Data Manipulation Language (DML) queries in SQL are used to manipulate and modify data within a database. Unlike Data Definition Language (DDL) queries that focus on defining and managing the structure of a database, DML queries are concerned with the actual data stored in the database. There are three main types of DML queries:

1. INSERT Statement:

   • The INSERT statement is used to add new rows or records to a table.

   • It can insert data into specific columns or all columns if values for all columns are provided.

   • Example: Inserting a new employee record into the "employees" table.

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     INSERT INTO employees (employee_id, first_name, last_name, hire_date)
     VALUES (101, 'John', 'Doe', '2023-09-01');
     
     

2. UPDATE Statement:

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

   • It specifies which table to update, which columns to modify, and the new values.

   • The WHERE clause is used to specify which rows to update; without it, all rows in the table are affected.

   • Example: Updating the hire date for an employee with the ID 101.

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     UPDATE employees
     SET hire_date = '2023-09-15'
     WHERE employee_id = 101;
     
     

3. DELETE Statement:

   • The DELETE statement is used to remove rows or records from a table.

   • It specifies which table to delete data from and uses the WHERE clause to determine which rows to delete.

   • Without the WHERE clause, all rows in the table will be deleted.

   • Example: Deleting an employee record with the ID 101.

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     DELETE FROM employees
     WHERE employee_id = 101;
     
     

DML queries are essential for maintaining and updating data in a relational database. They allow you to insert new records, modify existing data, and remove unwanted data. Properly crafted DML statements are crucial for ensuring data accuracy and integrity in a database-driven application.