DML (Datal Manipulation Language)

Data Manipulation Language (DML) is a subset of SQL (Structured Query Language) used to interact with and manipulate data stored within a database. DML commands are primarily focused on retrieving, inserting, updating, and deleting data records within database tables. Here are the main types and examples of DML commands:

1. SELECT:

The SELECT statement retrieves data from one or more tables in a database.

Basic SELECT:

This command retrieves all records from a table.

SELECT * FROM employees;

SELECT with Conditions:

You can use conditions to filter the results

SELECT first_name, last_name

FROM employees

WHERE department = 'HR';

2. INSERT:

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

• INSERT INTO:

  This command adds a new record to the employees table.

• INSERT INTO employees (employee_id, first_name, last_name, department)

  VALUES (1, 'John', 'Doe', 'Sales');

. UPDATE:

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

UPDATE:

This command updates the salary for employees in the Sales department.

UPDATE employees

SET salary = salary * 1.1

WHERE department = 'Sales';

DELETE:

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

DELETE FROM:

This command deletes all records for employees with the last name 'Smith.'

DELETE FROM employees

WHERE last_name = 'Smith';

MERGE:

The MERGE statement is used to perform conditional insert, update, or delete operations in a single statement. It's particularly useful for handling data synchronization.

MERGE INTO:

This example demonstrates merging data from a source_table into a target_table:------

     MERGE INTO target_table AS T

     USING source_table AS S

     ON T.id = S.id

    WHEN MATCHED THEN

    UPDATE SET T.value = S.value

    WHEN NOT MATCHED THEN

    INSERT (id, value) VALUES (S.id, S.value);