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Data Manipulation Language (DML) in SQL


  DML (Data Manipulation Language) in SQL is used to manage and modify data stored in databases. It includes essential commands like `INSERT`, `UPDATE`, `DELETE`, and `SELECT`.


DML Commands in SQL

  DML commands allow you to interact with data stored in database tables:


  • INSERT: Adds new records to a table.
  • UPDATE: Modifies data of existing records in a table.
  • DELETE: Removes specific records from a table.
  • SELECT: Retrieves data from one or more tables, allowing you to filter and sort the results.

  Next, we'll explain each of these commands with practical examples.


INSERT: Adding Data to a Table

  The `INSERT` command is used to add new records to a table. For example, to add a new employee to the `employees` table:

INSERT INTO employees (name, position, salary) 
VALUES ('Juan Pérez', 'Developer', 60000);

UPDATE: Modifying Existing Records

  The `UPDATE` command is used to modify data in existing records. For example, to update an employee's salary:

UPDATE employees 
SET salary = 65000 
WHERE name = 'Juan Pérez';

  This command modifies "Juan Pérez"'s salary to 65,000.


DELETE: Removing Records

  To remove records from a table, use the `DELETE` command. For example, to remove an employee's record:

DELETE FROM employees 
WHERE name = 'Juan Pérez';

  This command deletes "Juan Pérez"'s record from the `employees` table.


Using WHERE with DML

  The `WHERE` clause is very important when using `UPDATE` and `DELETE` to avoid accidentally affecting all records in a table. It's always recommended to use `WHERE` to specify the condition:

-- Update salary only for developers 
UPDATE employees 
SET salary = salary + 5000 
WHERE position = 'Developer'; 

-- Delete employees without an assigned position 
DELETE FROM employees 
WHERE position IS NULL;

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